Disk-Based Backup & Recovery: Making Sense of Your Options

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1 Disk-Based Backup & Recovery: Making Sense of Your Options White Paper Datalink September 2007 Abstract: Data and storage requirements are growing at unbelievable rates for businesses of every type. To help counter this, it s time for organizations to examine the benefits that disk storage subsystems can provide in data protection environments. This white paper details four enhanced data recovery (disk-based backup) architectures and provides guidance on how to determine whether or not those architectures would be an overall fit within the IT infrastructure. The assessment of a solution s effectiveness examines whether its overall benefits balance well against its human, corporate, and financial costs. This white paper offers in-depth insight on what those benefits and costs are so that IT professionals are armed with the knowledge required to make sound decisions.

2 Table of Contents Introduction Tape: the traditional approach to data recovery Why disk makes sense for data recovery now Paper topics Data recovery bottlenecks and their impact on recovery operations What is a bottleneck? Potential bottleneck areas Improper assessment of bottlenecks Eliminating bottlenecks with enhanced data recovery solutions What is enhanced data recovery? First analyze the pain points Can disk play a role? Will disk completely replace tape? The cost of archiving The cost of off-site media storage Disk is just another tool Enhanced Data Recovery Architectures Categories The enhanced data recovery continuum Disk to disk (D2D) How does D2D work? Synthetic full backups Challenges Operational benefits Best fit Business value impact of D2D Example of a D2D implementation Virtual tape How does it work? Vendor approaches to virtual tape Challenges Operational benefits Best fit Business value impact of virtual tape Example of a virtual tape implementation Point-in-time copies Types of point-in-time copies Full image mirroring technology Mirror management Snapshot edits, additions, and disk space requirements Challenges Operational benefits

3 Best fit Business value impact of point-in-time copies Example of a point-in-time copy solution implementation Continuous data protection What is continuous data protection? How it works Challenges Operational benefits Best fit Business value impact of CDP Example of CDP implementation Adding depth to enhanced data recovery Data deduplication Replication Summary Compromise no longer necessary Understand the bottlenecks and pain points Role of disk Technologies Partnership with Datalink

4 Introduction Tape: the traditional approach to data recovery For decades, organizations have protected critical, electronically stored data by making a second copy of the data on tape. Since then, incremental progress has been made in improving this process. Tape drives have grown in capacity and performance. Software has become more sophisticated, allowing creative ways to back data up faster, and using fewer resources. Tape libraries using robotic automation have become common, enabling lights-out backup operations in large environments. Storage area networks (SANs) enable tremendous scalability with robust performance. Ultimately, however, these advances have not kept pace with the business expectations placed on IT organizations, and therefore the market has screamed for enhancements. The sources of pain come from many areas, but they can be grouped into the following categories: Data growth While tape-based architectures have long been the primary technology of choice for backup and recovery, they have not kept pace with business exptectations placed on IT organizations. Backup windows Recovery time objectives (RTOs) Recovery point objectives (RPOs) Decentralization of data Rising costs and flat budgets Compliance requirements and legal discovery needs Why disk makes sense for data recovery now While tape-based architectures have long been the primary technology of choice for backup and recovery, they have not kept pace with the business expectations placed on IT organizations. When comparing the costs of raw ATA or Serial ATA drives to those of LTO tape media, the difference has been more than 10X in favor of tape in the past. In today s market, however, the gap has narrowed and low-end disk is now less than 2X the cost per gigabyte of tape storage. As a result, organizations are increasingly augmenting tape-based backup and recovery architectures with disk-based solutions, resulting in measurable performance, reliability, and manageability enhancements. It s important to note though that tape technology has not stood still, so further reduction in the relative cost between raw disk capacity and raw tape capacity cannot be counted on to drive down the overall cost of disk-based systems. Still, with rapidly declining disk prices and the introduction of low cost, relatively high-performance RAID-protected ATA disk subsystems, the storage industry is now spinning about enhanced data recovery (disk-based) solutions, which raises these questions: 2007 Datalink. All Rights Reserved. 1

5 How much performance improvement can be realized in data recovery utilizing disk? Now that the price of disk has made it a practical consideration for data recovery, is tape needed? Will recovery operations be simpler with disk? The answer to those questions is one that nobody wants to hear: It depends. There are many variables in storage environments; therefore, it requires an organization to assess its environment and carefully prioritize its business objectives based on that assessment. Implementing a data recovery solution that meets business objectives and SLAs, especially around restoring data, is a tremendous challenge for IT managers. For example, if an organization is unable to meet its internal and external SLAs, it could pay a hefty price for this shortcoming. These costs could include lost revenue, lost productivity, penalties and litigation costs, and degraded customer and business partner experiences and confidence. All systems, including data recovery systems, contain bottlenecks. When one is removed, another one often appears. Paper topics The topics in this paper include: Environmental variables (how bottlenecks impact data recovery operations) Enhanced data recovery approaches (how can new technologies be used to augment tape for data recovery?) Enhanced data recovery architectures (the categories, benefits, and best fit) Data recovery bottlenecks and their impact on recovery operations What is a bottleneck? In its broadest perspective, a bottleneck is the step or process within every system that imposes a delay on the ultimate throughput of that system. A bottleneck can exist in any area of a system, including people, process, or technology. All systems, including data recovery systems, contain bottlenecks. When a bottleneck is removed, another one often appears, or worse, another one is actually created by improperly addressing the original bottleneck. When determining if disk technology can be implemented to address data recovery bottlenecks by improving performance or reliability, it is vital to fully assess the entire data recovery operation, and accurately pinpoint where the bottlenecks occur. The goal is to systematically remove bottlenecks until service level agreements (SLAs) can be met and quality of service (QoS) goals are achieved Datalink. All Rights Reserved. 2

6 Potential bottleneck areas Bottlenecks can be found in data recovery operations in the following areas: Procedure Software capabilities and configuration Hardware capabilities and configuration LAN performance and saturation levels SAN configurations Improper assessment of bottlenecks Often bottlenecks are inaccurately diagnosed in one component or area of the data recovery operation. This leads to an investment to improve the capabilities of the problem component or area. However, due to improper diagnosis, the upgrade will not yield a net performance improvement because it was not the cause of the bottleneck. Enhanced data recovery enables the concept of backing up to disk and archiving to tape. For example, an organization finds that its tape I/O performance is not adequate during a backup operation, so it upgrades the tape drives. When the tape drive upgrade does not improve backup performance, the organization implements a SAN to increase the bandwidth to the drives. Still frustrated, the organization next replaces the host bus adaptors (HBAs) in the servers. The performance is still slow so the organization deduces that the issue must be the backup application. The organization upgrades the application and the problem still exists. Then the organization realizes that there are too many files in one directory. This directory bogs down the file system, preventing the server from sending data down stream any faster than previously. When the real bottleneck is fixed though, a new one appears. This new bottleneck might be resolved by introducing disk into the environment. But even if this were the case, disk as a backup target clearly would not have addressed the root cause of the problem (too many files in one directory), even if it provided some symptomatic relief. For that matter, any one of the introduced fixes could have exacerbated or further masked the true problem. This example illustrates the need for a systematic, objective-based approach to assessing problems that occur in data recovery operations. Eliminating bottlenecks with enhanced data recovery solutions What is enhanced data recovery? Enhanced data recovery is a data backup and recovery architecture that adds a disk-based storage array (combined with a sophisticated software technology) to a traditional tape-only solution. It enables the concept of backing up to disk and archiving to tape Datalink. All Rights Reserved. 3

7 First analyze the pain points Before deciding to introduce disk into the data recovery equation, it is important to analyze and prioritize objectives based on pain points, and then determine the desired outcome. Typical objectives for a disk-based enhanced data recovery project should come from the organization s pain points: Data growth. No organization is exempt from the pressures of managing, storing, and protecting the ever-increasing amounts of data. Backup window. Backup window is defined as the time available for IT administrators to slow down or stop production to perform data recovery operations. In today s 24x7xforever business, organizations are increasingly finding that their backup windows have become either extremely compressed or extinct. They no longer have the luxury of shutting down applications, or sending out s to users asking them to wait until further notice to login. Recovery time objective (RTO). RTO is the goal that the organization sets for the time it takes to fully restore an application with its data when a failure or data loss occurs. Business executives measure system downtime in terms of hours and dollars; IT managers measure it in terms of high blood pressure and gray hair. Either way, it is no secret that the costs are both extremely high and on the rise. When a system goes down and perhaps loses its data, there is an expectation that the system will be recovered within a reasonable amount of time. Business units and IT staff often debate what might be deemed reasonable, given the available technology and staff. Usually, when a RTO is established for a particular application, it represents an ambitious goal, placing strain on the IT staff. (See Figure 1.) Before introducing disk into the equation, it s important to analyze and prioritize objectives based on pain points. Recovery point objective (RPO). RPO is defined as the point in time at which data is recovered. For example, if a backup is performed at midnight, and the data is used to recover a system at noon the next day, the recovery point would be midnight. This is a measurement of the data loss between the last backup and the time of data loss or corruption. The practical approach to determining RPO for a given application would be to ask these questions: How much data can we afford to lose; and what is the investment cost to protect the data to that level? To fully establish this, it is important to estimate how much data is generated during an hour of production, and what would be the cost to recreate this data (if possible) when lost or corrupted. This information can help determine the risk-adjusted ROI for technologies to improve the ability to recover data to a more recent point in time. (See Figure 1.) Figure 1: The cost of a data protection solution is relative to how quickly an organization needs to restore the data and how much data it can afford to lose Datalink. All Rights Reserved. 4

8 Decentralization of data. In recent years, storage hardware costs have declined more rapidly than WAN bandwidth costs. And over long distances, latency issues may preclude centralization of resources. For these reasons, companies often decentralize data to provide adequate performance in remote offices, without requiring the costly bandwidth necessary to run data-intensive applications on centralized storage. This introduces a significant challenge to provide adequate protection for decentralized data. Many companies place tape resources at remote sites and designate the most technical person in that office to take responsibility to maintain the data recovery operation. This approach is prone to error, which could result in significant data losses. Rising costs, flat budgets, and static headcount. Virtually all IT organizations feel the pressure of too much data and not enough resources to manage and protect it adequately. The expectation is that IT organizations continue to deliver against SLAs that remain constant for data recovery, while the volume of data grows rapidly, without adding headcount. While tape provides a good archive solution for many organizations, it can become an operational bottleneck in environments with frequent simultaneous backup and recovery operations. This pressure fuels the cry for data recovery technologies that allow greater scalability in the data center within constrained IT budgets. Depending on the identified bottlenecks and the established objectives, disk technologies can be added to the data recovery equation in different ways. Compliance requirements and legal discovery needs. Data must be secure, unalterable, and in some cases immediately accessible in order to comply with a myriad of regulations. In addition, litigation support and e-discovery have emerged as major IT and business challenges. Can disk play a role? Clearly defined and prioritized project objectives based on the organization s pain points and an understanding of the performance bottlenecks within a data recovery environment serve as the foundation for determining whether disk can play a role in the data recovery operations. Depending on the identified bottlenecks and the established objectives, disk technologies can be added to the data recovery equation in many different ways. This can be done to achieve efficiencies in data recovery operations. Will disk completely replace tape? The answer is probably not yet. In most environments, disk will complement, rather than replace tape in near-term implementations. Tape is a low-cost alternative to disk in two areas: 1) Economic archive due to its low incremental cost and portability; and 2) Foundational offsite disaster recovery storage. The cost of archiving When organizations evaluate the cost of disk and tape, their comparisons often focus on the simple cost per gigabyte of storage. They often overlook the ongoing operational cost with each medium for a given application. For archival purposes, there can be a great premium in the costs of managing 2007 Datalink. All Rights Reserved. 5

9 disk compared to those for managing offline tape. When measuring cost factors for data stored on disk, organizations should consider: Power consumption costs linked with keeping the spindles turning and keeping systems cool Wear-and-tear on all components of the array Data center floor space General storage management costs linked to disks In contrast, archived tape offers: Greater portability Little power consumption Cheaper storage space Less management effort over the course of an extended archival life cycle The cost of off-site media storage Most organizations have procedures in place to rotate a third set of tapes to an offsite vault location mainly for use after a disaster, but also in the event of a double-media failure in the data center. While this procedure could be deemed expensive compared to not having a disaster recovery plan in place, it is often economical compared to having live data replicated to a disk array at a remote hot site. With this approach, the cost of the incremental disk to manage the process (in lieu of tape) could be nominal. However, the total cost of this approach would include disk, software, servers, adequate bandwidth, remote data center, and management costs. It s evident that disk is not the silver bullet, but merely one more tool that can be leveraged to improve data recovery operations. It is clear that the total cost of this approach can be expensive. This is true particularly if the capabilities of tape can adequately satisfy the organization s requirement for recovery time and recovery point performance in the event of a site disaster. Disk is just another tool It is evident that disk is not the silver bullet, but merely one more tool that can be leveraged to improve an organization s data recovery operations. If it is determined that disk should play a role, the next step would be to architect a solution that applies the right technologies to resolve the bottlenecks and to satisfy the data recovery pain points that the organization is experiencing. Enhanced Data Recovery Architectures Categories Datalink segments enhanced data recovery architectures into four categories: 1. Backup to disk, which is sometimes referred to as D2D (disk-to-disk) or D2D2T (disk-to-disk-to-tape). 2. Virtual tape, where software is used to present a virtual interface to disk, making it appear to backup applications as a tape device Datalink. All Rights Reserved. 6

10 Calculating ROI for a Tape Consolidation Project: Five Key Steps 3. Point-in-time copy, where an image of the data, such as a full mirror or pointer-based snapshot of the data is stored on a RAID subsystem. 4. Continuous data protection, which features the ongoing sequential capture of each data write transaction committed to a production volume. These transactions are held on a secondary disk volume with a logging feature that allows rolling back to a desired point in time. The enhanced data recovery continuum At a very basic level, data is protected by making copies of the production data. The method used to make these copies determines the level at which the data is protected as well as the costs required to reach that level. The enhanced data recovery continuum illustrates the range of methods available to deliver increasing levels of data protection. How quickly a copy can be made determines how often the copies occur, which dictates the maximum potential data loss. More specifically, all transaction records that are captured after the last copy was made are potentially lost if a disruption occurs. Because of budget limitations, most enterprises are not able to deploy the most sophisticated data protection solution available. Enhanced Data Recovery Continuum Recovery Point Recovery Time days hours seconds seconds hours days $ Cost of Protection $$$ $$$ Cost of Recovery $ $$$ Cost of Lost Data $ Failure Occurs $ Cost of Time $$$ Conventional Disk Virtual Tape Library Point-in-Time Copy Data Deduplication Replication Continuous Data Protection Figure 2: Organizations implement data protection technologies from somewhere on the con tinuum shown in the arrows above. Disk to disk (D2D) Because of budget limitations, most enterprises are not able to deploy the most sophisticated data protection solution available. Firms need to define an RPO and RTO for each of their applications and then select the most appropriate technology from a continuum of data protection technologies both disk and tape. How does D2D work? When backing up to disk, enterprise backup software directs data from server clients to a disk-based storage array. The data is stored on the disk before being staged or cloned to a tape library for secondary protection. Backing up 2007 Datalink. All Rights Reserved. 7

11 Primary Storage Backup to disk Slower (Secondary) Recovery Fast (Primary) Recovery Backup System Disk Staging can also provide an improved foundation for performing synthetic full backups. Tape Library Figure 3: Disk-to-disk recovery is fast and reliable. to disk benefits from the random access nature of disks, eliminating the slow sequential seek process of tape, which leads to faster file-level restores and improved reliability. (See Figure 3.) Synthetic full backups Backup to disk can also provide an improved foundation for performing synthetic full backups. Synthetic full backups allow organizations to perform one full backup, followed by ongoing incremental backups. These backups are finished by merging the full backup with the incremental backups as a background activity, resulting in an updated full backup. This stops the need to perform regular full backups, which can consume tremendous bandwidth and bring production to a grinding halt. Synthetic full backups can be done without using disk in a traditional tape environment, but the impact on resources during image consolidation backups can be significant. The wear and tear on tape and library resources from loading and unloading the tapes when backup images are regularly merged into a single set is significant. Also, tape technology does not allow multiple simultaneous reads or writes from a single tape or drive so any tape resource being used for synthetic full backup is unavailable during that period. Disk, however, can provide the server with online access to data for making merged backup images, minimizing the impact on tape resources. By storing the backup images onto disk, 2007 Datalink. All Rights Reserved. 8

12 these images are available for simultaneous reads for recovery operations during a synthetic full backup. Challenges Disk can yield improvements in a data recovery operation, but there are some challenges. First, to fully exploit the capabilities of D2D, it is critical that the backup application supports the desired functionality. Most commercial backup software products were originally designed to use tape as the exclusive backup medium. For most products, only recent upgrades make it feasible to use disk as a viable destination for backup data. Also, most file systems used to address disk were designed for random I/O; this is okay for general file access and database use, but not optimal for sequential, large-block data transfers, which is a common characteristic of backup applications. This introduces a bottleneck and throttles back the performance of the disk subsystem. Although this approach can yield backup performance benefits in some environments, its primary benefits are backup reliability and recovery performance. Another limiting factor to performance in a D2D configuration is the way most file systems reclaim and reuse space on a volume after data has been deleted. The file system will generally write new blocks of data to the locations where data has been deleted. This is done so that the blocks become available, without regard for where they are physically on the disk surface. This method of writing to disk causes a condition known as fragmentation and leads to performance loss, which worsens over time as the data on a volume becomes increasingly more fragmented. A third challenge is the cost of conventional disk, which has limited its use to only the most important data and the most recent backups. Acquisition costs for conventional disk have been high due to the lack of advanced storageefficient technologies. However, with the introduction of data deduplication technologies, the cost factor is significantly less and shows a strong ROI. Operational benefits In D2D backup, traditional disk storage often ATA or SATA based can be configured as the target for recovery data. By utilizing disk technology as part of a data recovery infrastructure, an IT operation can improve its ability to meet its backup windows, improve RTO, increase reliability, and provide greater functionality. Although this approach can yield backup performance benefits in some environments, its primary benefits are backup reliability and recovery performance. Datalink recommends that a copy of the data be written to tape or replicated offsite for disaster recovery and archive purposes. Best fit D2D recovery can give an organization a greater ability to meet its RTOs. This is noticeable when having to recover individual or small file sets on a regular basis. Depending on what bottlenecks exist in the environment, D2D can also improve the ability to meet a defined backup window. D2D also has a reliability advantage over tape, which can lead to some RPO benefit in an 2007 Datalink. All Rights Reserved. 9

13 environment with a high failure rate on backup jobs. When a tape backup job fails, the previous evening s backup becomes the recovery point, exposing up to 48 hours of potential data loss. In addition, D2D offers benefits in environments where backup is performed over low-performing or saturated networks and tape streaming is difficult to achieve, or where interleaving must be used to achieve streaming tape drives. In these environments, the data will be accepted by the recovery disk at whatever speed the data is delivered. This stops the shoe-shining effect (common to many low-end and mid-range tape drives), thereby greatly improving system throughput. Advantages can also be achieved in performance at the high-end of the spectrum, where disk offers greater data configuration flexibility on primary storage, such as with database systems. Once the system is optimized, disk can deliver performance comparable or greater than tape with less ongoing tweaking and tuning. Advantages can also be achieved at the high-end of the spectrum, where disk offers greater data configuration flexibility, such as with database systems. Business value impact of D2D In addition to the operational benefits within IT, organizations experience the following business benefits associated with the successful implementation of D2D backup: - Reduced risk to business viability due to unprotected data as a result of failed backups - Tape media cost savings due to reduced tape media consumption - Higher employee productivity due to shortened downtime in the event that data needs to be recovered from a backup source - Improved customer satisfaction as customers experience fewer outages from the business and their inquiries are answered more quickly because employees will have improved access to critical data Example of a D2D implementation Problem: A medium-sized IT services organization faced an ongoing challenge of lackluster backup operations performance. Due to complex application configurations and overburdened servers, the organization was unable to deliver data to its tape drives at a fast enough rate to stream the devices, which caused excessive wear and tear on the tape drives and media, and dramatically impacted the overall throughput of the system. Also, the tape duplication process for disaster recovery was unacceptably slow given the environmental limitations. As a workaround, multiplexing was implemented as a means of aggregating multiple data streams in an effort to stream the tape drives. While this offered some relief on backup operations, it had negative ramifications on restore performance due to the greater amount of interleaved data that needed to be read during a system restoration. Solution: Careful analysis of this environment identified multiple bottlenecks that could be addressed to improve the situation. Given a variety of 2007 Datalink. All Rights Reserved. 10

14 cost and implementation process variables, it was determined that the most cost effective option, and the measure that would also deliver the most benefit, was a D2D architecture. Secondary disk has been implemented as the initial destination for backup jobs. From that location, backup data is subsequently cloned to tape in a process that is controlled by the backup application. A copy of backup data is maintained on disk for a period of time where it is accessible for restore operations. Results: The implementation of D2D required some minor modification of the backup environment, but the overall effort was not excessive. The organization experienced roughly a 60% reduction in the amount of time necessary to complete a backup and a noticeable decrease in the wear and tear on tape resources, as the cloning process consistently results in full streaming of the tape drives. The system was architected so that approximately 90-95% of recoveries are sourced from disk. Tape recoveries are extremely rare. Diskbased recoveries occur much more quickly than tape recoveries, which allows the IT organization to meet its SLAs to the business units. The backup and recovery operation can be delivered much more consistently and requires 60-70% fewer administrative hours, leading to greater productivity within IT. Another approach to introducing disk into the recovery infraststructure is to use emulation technology as a frontend to the disk. Virtual tape How does it work? Another approach to introducing disk into the recovery infrastructure is to use emulation technology as a front-end to the disk system. This presents disk to the backup application in a way that makes it appear as tape. In many cases this approach (as shown in Figure 4) is the least disruptive of the four discussed in this paper. Fast (Primary) Recovery Tape Emulation Disk Primary Storage Backup System Server (Secondary) Recovery Tape Library Figure 4: Virtual tape is typically easy to integrate Datalink. All Rights Reserved. 11

15 Vendor approaches to virtual tape Vendors have taken a couple different approaches to bundling this technology and the role that it can play in the recovery operation. The following items characterize some of the differentiation in the marketplace: Integrated Virtual Library Solution: Several traditional storage vendors as well as new technology companies have integrated software, server, and disk into a packaged solution. This approach offers a pre-configured solution that has been integrated and tested with specific backup software and server platforms. It also provides a single point of support for the complete solution (i.e., one throat to choke). Software Only: Other virtual tape products come as a software-only solution. With this approach, the software is integrated on a customer or software vendor supplied server, with Fibre Channel cards and network connections.this allows the customer to choose the optimal server architecture for its data volumes, performance needs, infrastructure, etc. In addition, it provides the ability to select which open systems disk product best fits the environment. Several traditional storage vendors as well as new technology companies have integrated software, server, and disk into a packaged solution. This approach also offers the ability to utilize the newest software functionality available from the software vendor (features that are not yet included in the integrated VTL solutions). It can also support backup server platforms that are not yet supported in an integrated solution. Data Mover or Not: Virtual tape vendors take differing positions on whether the virtual tape technology should be a passive or active storage device. In the passive approach, the virtual tape technology allows the backup application and server to take responsibility for migrating data from disk to tape for archival purposes. In the active approach, it can manage this task with or without direction from the backup server. The benefit of having the backup server manage this I/O is that seamless command and control is maintained in the environment and the risk of having metadata and subsequent data integrity challenges in the backup application is minimized. The advantage of having the virtual tape product manage this data migration is that the I/O can occur without passing through the backup application server, which allows the server to perform its other tasks without being impacted. Current best practices favor leaving the backup application in charge of all data movement from disk to tape to simplify management and assure metadata integrity. Challenges Virtual tape is a mainstream solution with many vendors offering products that support this capability. Caution must be taken to ensure that all backup applications in the environment support this technology. Also, the virtual tape technology should provide the ability to emulate a tape resource that is appropriate for the targeted environment Datalink. All Rights Reserved. 12

16 Another factor to consider is that efficient use of tape may be minimized when moving data from virtual to physical tape, depending on the backup application and how it leverages compression. Operational benefits Virtual tape offers all the same benefits of D2D and addresses some of its shortcomings. It enables seamless integration of disk into the data recovery operation versus D2D, which generally requires some re-engineering of the data recovery workflow. In some highly complex customized environments, virtual tape makes it possible to consider using disk as a backup destination, as the effort to modify all the scripts needed to use standard D2D would be far too disruptive. virtual tape can result in measurable performance gains versus D2D. This is because it does not have the same file system overhead and disk fragmentation typically associated with disk systems. Another reason is it enables data to be transferred to disk in large blocks, similar to how data is typically written to tape, rather than small blocks more typically associated with transfer to standard disk. And since disk systems are random access devices, the importance of maintaining streaming performance, which is critical to tape system performance, is eliminated. The optimal environment for virtual tape is one that has a considerable level of customization to the data recovery workflow. Best fit In assessing the best fit for virtual tape technology, it is important to note if the technology is being compared to tape or D2D. For this discussion, the attributes of virtual tape are compared primarily with those of a D2D architecture. The optimal environment for virtual tape technology is one that has a considerable level of customization to the data recovery workflow, where the introduction of standard D2D would be too disruptive. Other characteristics of an environment that would lead to the introduction of virtual tape include: Intense backup window pressure and a strong requirement for improved performance, where disk fragmentation of standard D2D would be a consideration Preservation of investment in existing backup software and tape systems Use of disk and tape in a tiered backup strategy Reduction of reliance on physical tape (physical tape archived off-site for disaster recovery) Need for quick restore of recent backups Need for additional tape resources to eliminate tape device bottlenecks 2007 Datalink. All Rights Reserved. 13

17 Business value impact of virtual tape As a starting point, organizations can expect to receive the same business benefits as with D2D. In addition to these, companies may also experience: Lower IT expense for the initial implementation due to the ease of implementation relative to D2D Improved user access to production data resulting in greater productivity as a result of backups completing more quickly Lower ongoing IT expenses due to simplified file system administration and centralized volume management Example of a virtual tape implementation Problem: A large international food distributor was facing extreme pressure in its data recovery operations. With over 35 terabytes of production data, the organization struggled to meet its backup windows and recovery SLAs. Scheduled full backups were cancelled frequently for production purposes. As a starting point, organizations can expect to receive the same business benefits as with D2D. Nightly backups were failing at rates of 10 to 15 percent, which required a full-time system administrator to troubleshoot the failures. Often cloning operations or recovery operations conflicted with backup jobs. Recoveries took from hours to days, depending on the data source and the number of lost or corrupt files. Backup windows were stretched and the environment required significant tuning through use of techniques like multiplexing to maintain backup system performance. Solution: The assessment of this environment led to the determination that traditional tape technology imposed many limitations that caused performance and reliability problems. Disk-to-disk recovery seemed like the natural solution to some problems, but due to the customized backup application, the implementation would be difficult and too disruptive. Also, without compression capabilities, the amount of disk required to support this application would be cost prohibitive. Further analysis showed that a virtual tape solution was the best fit. This approach eliminated the need to modify the customized workflow that was continually optimized over the years and provided file compression capability to minimize the amount of disk space required to enable the solution. Results: Backups are consistently completed within the backup window, with nearly 100 percent reliability. Data recoveries occur within established SLAs. The implementation was completed with minimal disruption to the customized workflow; also, the full-time administrator previously dedicated to troubleshooting failed backups was re-assigned to other proactive storage projects Datalink. All Rights Reserved. 14

18 Point-in-time copies Types of point-in-time copies Point-in-time copy software makes a mirrored copy of the production data, which is split off and assigned to a backup server. This is referred to as off host or zero impact backup since the application server is not responsible for performing the backup. Two types of copies exist: full image and pointerbased copies. Full image mirrors are complete block-level copies of the original data. Pointer-based mirrors are copies of the index information identifying where data exists on the storage array. Full image mirroring technology Many storage infrastructures include component redundancy such as disk mirroring, using RAID 1 to improve the reliability and availability of primary disk storage subsystems. Often organizations take advantage of mirroring technology to augment their recovery capabilities. By deploying an additional mirror, this tertiary copy of the data can be separated from the primary and the first mirror for data recovery operations. This provides a point-intime copy of data, which is separate from application and user data. A separate server can backup this copy without adversely affecting production on the application server. (See Figure 5.) Point-in-time copy software makes a mirrored copy of the production data, which is split off and assigned to a backup server. Mirror management Mirror management can be performed by either hardware or software-based utilities with similar benefits to data recovery operations. One advantage of using software-based volume administration to manage the point-in-time copy of the data is that inexpensive storage media can be used for second mirrors. This allows organizations to invest in innovative RAID technology for production storage, while using less expensive storage subsystems. Organizations can also use repurposed legacy storage for their second mirrors, where performance and availability are not as critical as with production storage. Pointer-based snapshot technology Pointer-based snapshots are copies of the index information identifying where the data resides on the storage array. Snapshot technology provides a means of creating parallel, read-only file systems that point to a set of data intermingled with live-production data. Creating pointer-based snapshots take only seconds with minimal impact on the system. There are two general categories of pointer-based snapshots: file system and storage array. File system snapshots are stored as small files on the live file system. The data that exists at the time of the snapshot is protected from being overwritten on the physical disk, so that it can be referenced from the snapshots. This enables consistent static access to files at an identified point in time, which offers tremendous benefit to data recovery operations Datalink. All Rights Reserved. 15

19 Production Server It is important to Data Mirror Production splits off a mirror copy of the data. The mirror is mounted to a second server, where the data is backed up without impacting the production server. After backup, data can be resynchronized with the primary data volume. manage and cycle the snapshots so the unneeded disk space can be released and made available to the live file system. Mirror Backup Server Figure 5: Data mirroring Storage array snapshots create a designated area on the LUN where new data is written in a copy-on-write operation, when data is updated on the LUN. This allows quick rollback to a point in time, but adds overhead to the process of updating data on the array, given that one read and two writes need to occur for each updated block, compared to only one write in a file system snapshot environment. Snapshot edits, additions, and disk space requirements Data edits and additions are written to a new area on the disk, which means that snapshots do not require nearly the incremental disk space required for point-in-time data copies (split mirrors), but generally some incremental disk space is required. The disk space requirement is dependent on two factors: The length of time the snapshots are kept The data refresh rate It is important to manage and cycle the snapshots so that the unneeded disk space can be released and made available to the live file system. (See Figure 6.) Snapshots and the data recovery process Snapshots of data can be taken either to create a consistent point of quick rollback for inadvertent changes, deletions, or corruption of the data or to establish a solid point-in-time reference to a live data source to assist data 2007 Datalink. All Rights Reserved. 16

20 Base Data Creates snapshot of base data and a snapshot directory with pointer to data at point in time Writes new blocks, updating base data; points to base blocks in snapshot directory Data Data Snapshot Data Snapshot For recovery purposes, snapshot Snapshot Directory 2 New blocks will not be overwritten Snapshot Directory Directory points to data changed in base data Figure 6: File system data snapshots recovery operations. When snapshots are used as part of the backup, a snapshot of the data is taken before the backup process begins. Then the data host mounts the read-only snapshot file system for backup purposes, while continuing its production use of the live file system. The potential drawback of this approach is that it creates a lot of I/O activity on the primary volume, which can impact the performance of a production application. This is an advantage for full-image point-in-time copies. file systems can be referenced to recover files that have been corrupted or inadvertently deleted. For recovery purposes, snapshot file systems can be referenced to recover files that have been corrupted or inadvertently deleted. In many environments, snapshot technology is used for up to 90 percent of file recovery, rather than retrieving the file from tape or other secondary media. This recovery method greatly improves performance, eases administration, and serves to complement traditional recovery technologies. Snapshots also provide IT organizations the ability to deliver on the most stringent RPO requirements related to recovering corrupted or deleted files. Challenges One challenge that exists with snapshot technology is the management of file system and storage array snapshots. These technologies can generate countless snapshots. This is good because snapshots offer such a dramatic RPO improvement over traditional tape backup, but they do not offer a good centralized method of systematically generating, managing, and releasing the snapshots. This seems to be a new battleground for backup software products, as these vendors recognize the value of incorporating this management intelligence into the traditional backup application interface. As this capability is incorporated into the environment, it allows centrally managing snapshots consistently across all storage platforms. A second challenge is that snapshot implementations can cause a heavy hit on network performance. Backing up at the byte or block level is substantial Datalink. All Rights Reserved. 17

21 ly more efficient versus copying an entire file. An optimal solution makes light demands on performance and works not only for remote offices but for the data center as well. Operational benefits This solution offers very fast full data recoveries, a decrease in network traffic, and backup times that are reduced to minutes. It reduces the organization s recovery time capability to hours versus days and helps consolidate backup software licenses. Best fit Off-host backup provides a method for delivering quality, predictable, pointin-time data protection, using standard data recovery technologies. Given the declining cost per megabyte of disk storage, this approach is gaining popularity as a way of performing backups without hindering production operations in environments with shrinking or non-existent backup windows. Off-host backup delivers quality, predictable pointin-time data protection using standard data recovery technologies. Business value impact of point-in-time copies Point-in-time copies deliver the following business benefits: Reduced risk of lost intellectual property due to data loss, given the capability to generate frequent snapshots Higher employee productivity due to shortened downtime in the event that data needs to be recovered from a backup source due to fast accessibility of point-in-time snapshot data Reduced IT labor costs as less time is spent recovering data given the fast nature of snapshot recovery Improved customer satisfaction as customers experience fewer outages from the business, and their inquiries are answered more quickly on average given that employees will have improved access to critical data Example of a point-in-time copy solution implementation Problem: A large organization ran its production systems on servers with direct-attached enterprise RAID storage subsystems. The data recovery method was to simply attach tape devices to each file server. The total file storage was roughly 20TB. A full backup cycle could take up to 40 hours and nightly incremental backups would consistently extend into the next business day. The environment lacked high availability; often, recovery from outages and data losses would take days due to high capacity and slow, legacy tape technology. Solution: A high availability, high performance, well-protected solution was installed to address these problems. The solution comprises file servers (as before), but in a clustered configuration, redundantly attached to two enterprise RAID subsystems with Fibre Channel and Serial ATA drives. The Fibre Channel drives house the production file shares while ATA storage provides 2007 Datalink. All Rights Reserved. 18

22 mirrored copies that are systematically split from the production data for off host backup. For tape backup, a group of servers running data protection software was installed. Every night, these servers get a copy of the production data from FC LUNs. Clone copies are written to ATA RAID LUNs. The servers mount the ATA volumes containing a replica of the production data. Backup servers write that data via a FC SAN to an enterprise tape library subsystem. The two tape copy writes of the data are written simultaneously for immediate offsite storage. Mirror copies remain mounted on the backup servers until the next backup cycle, which provides for direct network-share recovery and a test platform for patches, software, etc. Results: Full backups have gone from 40 hours to just seconds, in terms of the time that production is impacted. The high availability capabilities have significantly reduced service outages and the risk of data loss. If a data loss were to occur, an exact replica of production data would be ready for full volume-level recovery. Primary recovery has gone from slow, outdated tape technology to a simple network share via the backup servers, housing the previous day s data. Users simply drag and drop files or folders as a means of recovery. Volume recovery has gone from roughly 10 to 12 hours to minutes with mirror reverse synchronization and four to six hours if tape needs to be used. CDP is a front-end protection system that is always on, operating unobtrusively to enterprise applications. Continuous data protection What is continuous data protection? Continuous data protection (CDP) is a relatively new, emerging technology designed to continuously capture or track data modifications and store changes independently of the primary data, enabling recovery points from any point in the past. In effect, CDP creates an electronic journal of complete storage snapshots, one storage snapshot for every instant in time that data modifications occur. A major advantage of CDP is that it preserves a record of every transaction that takes place in the enterprise. CDP can support RPOs of zero as well as protect against data corruption errors because data can be rolled back to the exact instant before the error occurred. The working definition for CDP from the Storage Networking Industry Association (SNIA) CDP Special Interest Group is a methodology that continuously captures or tracks data modifications and stores changes independently of the primary data, enabling recovery points from any point in the past. CDP systems may be block, file, or application-based and can provide fine granularities of restorable objects to infinitely variable recovery points. How it works CDP is a front-end protection system that is always on, operating unobtrusively to enterprise applications. A typical CDP system is based on a disk storage infrastructure to log the continuous data changes as well as provide a time-indexed view into historic points in time. As such, CDP systems may 2007 Datalink. All Rights Reserved. 19

23 Application Server Application Server Application Server Application Server Application Server Application Server Source Vol SAN Source Vol Journal Site 2 is for site 1 disaster and provides instant failover CDP is a front-end protection system that is always on, operating unobtrusively to enter- Copy of every change Journal Instant restore to last written change Target Vol prise applica- Storage Array Site 1 Storage Array Site 2 tions. Figure 7: Continuous data protection require additional processing resources depending on the approach. In return, CDP can provide enterprise IT organizations with seamless, near-instantaneous recoveries from logical and physical data corruption events stemming from many sources, including operator errors. Recovery can be in seconds or minutes rather than the hours that a traditional application and data restoration operation may entail. Challenges The challenges with implementing a CDP solution include: Managing complexity. Because of the number of heterogeneous products often involved, it is important to select a CDP solution that minimizes the number of interfaces data administrators must master. Otherwise, the volume of point product interfaces involved will rapidly transform simplified environments into ones that are vastly more complex. Designing reliability and availability. With the aggressive RPO requirements, many factors must be considered and architected into the solution. These include dual paths, ensuring read/write acknowledgements, asynchronous versus synchronous replication, etc. Changing business practices. Often a CDP solution requires IT and business process changes to support the new technology or empower endusers to restore files. Maintaining financial responsibility for a CDP solution. IT must be diligent in selecting which data to protect. While it would be ideal to protect all data through a CDP solution, it is often not fiscally practical, so the EDR continuum must be leverage to select the most appropriate technology for different applications based on the RPO and RTO requirements Datalink. All Rights Reserved. 20