Engineering White Paper Backup-to-Disk Guide with Computer Associates BrightStor ARCserve Backup Abstract This white paper describes how to configure EMC CLARiiON CX series storage systems with Computer Associates BrightStor ARCserve Backup for optimal performance when backing up to disk. Published 6/12/2006
Copyright 2003, 2004, 2006 EMC Corporation and Computer Associates. All rights reserved. EMC and Computer Associates believe the information in this publication is accurate as of its publication date. The information is subject to change without notice. THE INFORMATION IN THIS PUBLICATION IS PROVIDED AS IS. EMC CORPORATION AND COMPUTER ASSOCIATES MAKE NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WITH RESPECT TO THE INFORMATION IN THIS PUBLICATION, AND SPECIFICALLY DISCLAIM IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Use, copying, and distribution of any EMC or Computer Associates software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com. All other trademarks used herein are the property of their respective owners. Part Number H864.3 Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 2
Table of Contents Introduction...4 Summary...4 Disk Backup Overview...4 Advantages of Backup to Disk... 5 Backup Performance... 5 Recovery... 5 Multistreaming... 5 Media Reliability and Data Availability... 5 Overall IT Efficiency... 5 Backup-to-Disk Performance Factors...6 RAID Types... 6 Striping... 6 Performance Factors... 6 File-System Block Size... 6 Windows File-System Tuning... 6 Solaris File-System Tuning... 7 CLARiiON Configuration Settings... 7 Storage-System Cache Settings... 7 Storage-System Element Size... 7 LUNs per RAID Group... 7 Recommendations for ATA Disk-Based Backups... 8 EMC CLARiiON Storage Systems...8 ATA Technology... 9 Computer Associates BrightStor ARCserve Backup...10 Device Configuration (Disk-Based)... 10 Device Configuration Window... 2 Testing Environment/Dataset Description... 3 CLARiiON/BrightStor ARCserve Backup and Restore Performance... 4 Aggregate Performance... 5 Conclusion...5 Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 3
Introduction This white paper explains implementing a backup-to-disk solution with EMC CLARiiON storage systems and Computer Associates BrightStor ARCserve Backup. The information in this paper provides backup administrators and technical consultants with specific configuration and parameter settings for both CLARiiON storage and BrightStor ARCserve Backup software to ensure optimum performance of disk backups. The solution outlined in the paper has been tested and is endorsed by EMC and Computer Associates. Summary Disk-based data protection solutions have become desirable and affordable due to the lower cost of Advanced Technology-Attached (ATA) storage systems. As a complement to using tape for long-term storage, backup to disk is a powerful solution for rapid recovery of mission-critical data, and yields significant benefits over traditional backup to tape with the promise of: Faster backups Rapid restores Near-term recovery of mission-critical data Greater reliability and predictability of the backup medium Significantly enhanced business continuance ATA disk technology implemented in CLARiiON storage systems is a key enabling technology for backup to disk, and provides significant backup and restore capabilities over traditional tape solutions. Disk-based backups do not replace tape, but instead shift tape into a more archival role. Today, EMC recommends adopting a backup-to-disk solution when backup and restore performance and data reliability are primary concerns. Disk Backup Overview Backup-to-disk means writing to a disk file in a file system. This capability is resident within BrightStor ARCserve Backup today. The file system may be on a Windows or Linux platform, depending on the backup server. The overarching premise is that all primary backups are targeted to be done to disk enabling significantly faster backups to occur, and even more importantly, providing for near instantaneous restore should the need arise. Under BrightStor ARCserve Backup policy control, data can be duplicated or migrated from disk to tape or other archival media as business service levels dictate. In the solution defined in this paper, disk storage resources are used for the primary or initial backup target, while tape resources are reallocated to the task of performing longer-term data retention needs. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 4
Advantages of Backup to Disk Traditionally, tape has been the backup medium of choice due to its cost-per-mb advantage over disk. However, the economics of ATA disk are narrowing that gap. The advantages of using disk over tape with backup solutions can be grouped into four major categories: Faster backup performance Faster recovery Improved media reliability and data availability Efficiency Backup Performance BrightStor ARCserve Backup users can back up data at the write speeds of CLARiiON storage systems. Additionally, disk drives are random-access devices and can immediately start writing data. Tape technologies require positioning and respond to a minimal data stream by shoe-shining or excessive positioning. Recovery Data is recovered at the processing speed of the CLARiiON storage system and is read in a contiguous manner, enabling users to gain the benefits of protecting clients in parallel without sacrificing recovery performance. Tape mounting and unmounting delays are also eliminated. As a result, BrightStor ARCserve Backup and CLARiiON users experience significant improvement in recovery time from disk compared to tape. Multistreaming Multistreaming improves CLARiiON aggregate performance by being able to read and write multiple streams of data to the same LUN simultaneously. Media Reliability and Data Availability Media-specific errors, including faulty tape media and tape mounting failures, which can cause backups to fail, are minimized. Disk-system RAID protection also ensures data availability in the event of a disk drive failure. The CLARiiON is a high-availability disk storage system with no single points of failure. As a result of the availability improvements, fewer full backups may be required, which saves network and CPU-processing cycles. Overall IT Efficiency Tape handling is reduced or eliminated. Maintaining a set of tapes from tape libraries can be problematic and requires properly trained personnel. Disk does not require the tape handling/positioning. Backup to disk also provides the ability to perform both backups and restores at the same time unlike a tape device or tape library. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 5
Backup-to-Disk Performance Factors This section describes the specific parameters that the user can alter to improve performance of backup to disk. EMC varied these parameters to determine recommended settings for optimum performance when backing up to a disk file. RAID Types CLARiiON storage systems use RAID technology to combine disks into one logical unit (LUN) to improve reliability and/or performance. CLARiiON arrays support RAID 5, RAID 3, RAID 1, RAID 0, and RAID 1/0. EMC recommends RAID 3 for backup-to-disk-specific applications. RAID 3 (with CLARiiON rev 13 code and higher) has been optimized with the CLARiiON storage system to provide excellent read/write performance with ATA technology. Testing showed the RAID 3 configuration outperformed all other RAID types in specific backup-to-disk applications (Release 13). Striping RAID 4+1 and 8+1 groups provide very comparable overall storage system performance especially when comparing performance based on total available storage capacity. RAID 4+1 groups are recommended in most customer environments. Performance Factors File-System Block Size Operating systems allocate space for files in blocks. The file-system block size varies depending on the OS being used. A larger file system block size provides a large I/O size, which can increase the bandwidth of a backup. Larger block sizes may also reduce file system fragmentation, which can impact the backup bandwidth. The source file system (the file system being read for backup) should be as defragmented as possible. This helps the backup utility to perform read requests more sequentially. The default file system block size for UFS, the native Solaris file system, is 8 KB. UFS can be configured with either 4 KB or 8 KB. EMC recommends that the defaults be used. Windows File-System Tuning Windows systems create a 63-sector hidden area on disk to house the Master Boot Record (MBR). This causes all I/O in the file system made on the subsequent partition to be misaligned (not on a 256 KB boundary), and therefore I/O performance suffers. When creating a LUN for use in a Windows system, enter a value of 63 in the offset field. This will correct the alignment. Another way to correct this is by using a program called diskpar, available on the Windows 2000 Resource Kit. Using diskpar, the user can alter the number of hidden blocks to a larger number so that the storage-system I/Os are aligned and better optimized. The disk defrag tool included in Windows 2000 will not work with cluster sizes greater than the default cluster size of 4 KB. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 6
Solaris File-System Tuning There are two possible values to tune with Solaris. The first is to ensure that maxcontig for the file system is set high enough. If it is not, rotational delays will be incurred when laying down all the sectors in the write. Set maxcontig to the maximum number of sectors in a write. EMC recommends setting maxcontig to 256 (equivalent to 128 KB since there are 512 bytes in a sector). The maxcontig value may be set when making a file system (such as with newfs) or later with tunefs. The second value to tune is the maximum number of bytes that can be written in a single I/O. This default value is 128 KB or 256 KB, depending on the hardware on which Solaris is running. There is little reason to go to 256 KB because the backup software would have to change to take advantage of the larger I/O size. For completeness, this line may be added to allow 1 MB I/O: set maxphys=1048576 CLARiiON Configuration Settings Storage-System Cache Settings CLARiiON storage-system caching improves read and write performance in two ways: For a read request: The storage system senses sequential reads from the host, and then starts to prefetch data from the back end into the read cache. The host then reads the data from cache. For a write request: Incoming host write requests are written to cache and then mirrored to the second storage processor. The host request is then acknowledged. Writing the data to the cache results in a faster response time. If the request modifies the same page in the write cache that has not yet been written to disk, the storage system updates the information in the cache before writing it to disk. Testing demonstrates that backup performance with cache off is reduced, even when the writes are aligned on the proper boundaries (such as 256 KB). EMC found minor effects on performance when varying the amount of memory dedicated to write cache. Similarly, when varying the high and low watermarks, there was little noticeable effect. EMC recommends enabling write cache. Storage-System Element Size The element size of a RAID device is defined as some number of 512-byte sectors. The element size defines the RAID group's stripe size, which can impact the behavior and performance of a RAID device. The default element size for a CLARiiON RAID device is 128, which is 64 KB. A five-drive RAID device has a stripe size of 256 KB. Algorithms in FLARE optimize back-end writes to a RAID 3 device. This type of optimized back-end I/O is termed MR3 writes. EMC recommends using the default RAID element size for devices that will be used for backup-todisk devices. LUNs per RAID Group Testing has demonstrated that multiple data streams (reading or writing) to an ATA RAID group provide maximum aggregate performance. Data streams can be a combination of multiple streams to a single LUN, or single streams to multiple LUNs all within a single RAID group. EMC recommends total stream counts not exceed five streams to a single RAID group. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 7
Recommendations for ATA Disk-Based Backups The following disk-based backup guidelines should be used when planning CLARiiON backup-to-disk configurations: Use a five-disk RAID 3 configuration. Enable write cache. Set the page size to 16 for optimum performance. EMC CLARiiON Storage Systems CLARiiON storage systems provide leading performance, scalability, and investment protection. These storage solutions feature modular building blocks, based on advanced sixth-generation Fibre Channel technology. EMC Fibre Channel CX series disk-array storage systems provide terabytes of disk storage capacity, high transfer rates, flexible configurations, and highly available data at affordable price points. Hardware RAID features are provided by two storage processors (SPs). Figure 1. CLARiiON CX Series Overview Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 8
ATA Technology EMC has implemented ATA disk technology into existing CLARiiON CX series storage systems. The economics of ATA enable customers to keep more data online for longer periods of time. For many, previous alternatives were not affordable or justifiable. Customers can now mix and match performance Fibre Channel drives and capacity ATA drives within the same storage system, under common management, supported by the complete CLARiiON software suite. This single storage-system implementation provides considerable deployment flexibility. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 9
Computer Associates BrightStor ARCserve Backup BrightStor ARCserve Backup delivers enterprise-class backup/restore protection for distributed Intelarchitected enterprises. Based on the Windows, NetWare, and Linux platforms, BrightStor ARCserve Backup protects the major distributed server and workstation platforms in use today, and delivers ease of use, reliability, scalability, and innovation. With a wide range of options and system, database, and messaging agents available, the solution can be customized to meet individual systems requirements. A wide variety of industry-standard components are used with BrightStor ARCserve Backup on EMC CLARiiON storage systems in a storage area network (SAN). Each component is tested within a SAN environment to ensure its reliability and interoperability. This testing assures customers that their backup solution will work. Device Configuration (Disk-Based) CA BrightStor ARCserve Backup incorporates disk backup as file system devices. File system devices must first be configured in BrightStor ARCserve Backup s Device Configuration GUI in order to write to a disk file. Each file system device is a specified Windows folder. A device group may include a number of file system devices. Backup will migrate to another file system device when one is full. Figure 2 illustrates how to configure a CLARiiON file system device for backing up to disk. Figure 2. BrightStor ARCserve Backup Device Configuration Screen Select File System Devices, and then click Next. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 10
Figure 3 shows the screen where a destination for the folder on disk is selected. Figure 3. BrightStor ARCserve Backup Destination Screen Device Configuration Window Once the setup procedure is complete, the configuration can be viewed from the BrightStor ARCserve Backup Device screen. Figure 4 shows the information on a CX400 storage system. Figure 4. BrightStor ARCserve Backup Device Screen Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 2
Testing Environment/Dataset Description The CX series storage systems were tested in a backup-to-disk Windows 2000 and Windows 2003 environment to determine and characterize total aggregate performance when using ATA disk enclosures. The CX700 was configured with five ATA DAEs (75 disks). The CX500 was configured with five ATA DAEs (75 disks), and the CX300 was configured with three ATA DAE (45 disks), which is the maximum number of ATA drives supported in a CX300 storage system. Each LUN was placed on alternate SPs to balance the system workload. System settings: Page size was set to 16 (default was 8) Cache assignment on the CX700 was 2048 MB for write and 1024 MB each for the read cache Cache assignment on the CX500 had 50 MB each on the read cache and the remaining (net) on write cache (568 MB) The CX300 was configured with 20 MB each on the read cache and the remaining memory on write cache The source data was on a separate CX700 configured with six Fibre Channel DAEs (90 disks). Up to four Windows servers were used to send data to the storage systems to measure total aggregate performance. Each host had both source and destination LUNs configured. Two FC switches were used with each host having two FC HBAs. The CX700 and CX500 had two FC connections per SP attached. Performance testing consisted of 4+1 RAID 3 configurations. Each RAID group had one LUN assigned to it. Large dataset (12 GB): Small dataset (directory is 503 MB): 1 GB size files 3 files 50 KB size files 10,000 files 100 MB size files 60 files 10 MB size files 600 files 1 MB size files 3,000 files CX700 CX300 CX500 EMC DS-16B2 FC Switches Figure 5. Backup-to-Disk SAN Testing Configuration Diagram Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 3
CLARiiON/BrightStor ARCserve Backup and Restore Performance CA BrightStor ARCserve ATA Performance Results 100 90 80 70 60 MB/s 50 40 30 20 10 0 CX700 CX500 CX300 Backup Restore Figure 6. CLARiiON Performance with BrightStor ARCserve Backup Figure 6 depicts single-stream performance of backing up and restoring to ATA disk. The chart shows throughput while data is being transferred. Performance comparisons with tape devices would have to take into account tape positioning, file seek times, library mechanical load/unload times, etc., in addition to the typically slower transfer speeds of tape technology. BrightStor ARCserve Backup can compress data for disk-based backup via software. Testing found that performance suffers significantly when enabling this option. EMC recommends software compression be turned off when trying to optimize backup to disk performance. In cases where conserving disk space is critical, compression may be enabled. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 4
Aggregate Performance Total aggregate performance of the CLARiiON storage system varies depending on the type of CLARiiON storage system used, the type of backup host, file system, and nature of the data. Expect a maximum-per- LUN throughput of 60 MB/s to 65 MB/s when only one backup stream to a LUN (RAID group) is active for a CX700 storage array. As more backup streams, RAID groups and LUNs/RAID group are added and running simultaneously, total aggregate performance of the storage system will substantially increase. Refer to EMC s CSPEED organization for detailed multistream backup- to-disk performance information. Conclusion Backup-to- disk is an implementation that offers service-level improvements over the traditional tape backup process. With the changing economics of disk technology, backup-to-disk solutions are now affordable and customers are implementing backup-to-disk solutions as improvements to their existing tape solutions. Many variables can be set within the CLARiiON storage system and BrightStor ARCserve Backup to optimize backup-to-disk performance. EMC recommends using ATA technology to optimize backup performance with BrightStor ARCserve Backup. Major advantages of backup to disk include: Faster backup performance Faster data recovery Improved media reliability and data availability Improved IT management and efficiency To ensure optimum backup-to-disk performance: Enable CLARiiON write cache. Use only RAID 3 striping for backup to disk with CLARiiON arrays. RAID 3 has been optimized for read/write performance with cache enabled and ATA technology. Configure all RAID groups as 4+1 stripes. Ensure source file defragmentation. Limit the number of backup streams/raid groups to no more than four to five. Set file system block and element sizes to their default settings. Set Windows and Solaris operating system parameters as outlined on page 7. Disable software compression where possible. Note: When configuring CLARiiON storage systems for backups, create five-disk RAID 3 configurations. Exclusive LUNs within the RAID group must be assigned to each backup system/server. Multiple systems/servers can share CLARiiON storage systems as long as each server has exclusive use of one or more LUNs in the storage system for backup operations. Backup-to-Disk Guide with CA s BrightStor ARCserve Backup 5