Backups and archives: What s the scoop?

Transcription

1 E-Guide Backups and archives: What s the scoop? What s a backup and what s an archive? For starters, one of the differences worth noting is that a backup is always a copy while an archive should be original that was removed from its primary location and sent somewhere for long-term data retention. Check out this expert E-Guide to learn more about the differences between a backup and an archive. Also discover five of the most common IBM Tivoli Storage Manger backup errors and how to prevent them. Sponsored By:

2 E-Guide Backups and archives: What s the scoop? Table of Contents Backup vs. archive Five IBM Tivoli Storage Manager backup errors and how to prevent them Resources from IBM Sponsored By: Page 2 of 10

3 Backup vs. archive By Pierre Dorion When discussing the difference between backups and archives, we should probably start with introducing some generally accepted definitions for the terms "backup" and "archive." I use the "generally accepted" qualifier because in IT, terminology is rarely absolute. Furthermore, the world of IT is full of smart people and smart people like to argue a lot. Backup: A backup refers to a copy of data that may be used to restore the original in the event the latter is lost or damaged beyond repair. It is a safeguard for data that is being used. Archive: An archive refers to a single or a collection of historical records specifically selected for long-term retention and future reference. It is usually data that is no longer actively used. One of the differences worth noting in the above descriptions is that a backup is always a copy while an archive should be the original that was removed from its initial location and sent elsewhere for long-term retention. Frequently, backup software is configured in an attempt to fulfill both roles. Data backup schedules often include daily incremental backups kept for seven days, a weekly full kept for a month, a monthly full kept for a year and finally, a yearly full kept for seven years. The yearly full backups are often referred to as seven-year archives. The problem with that scheme is that it becomes very difficult to single out specific files for long-term retention out of an entire backup job, so a user of this method often ends up having to lump everything into on large "archive" package, which is a full backup. Some programs allow you to create so-called archives from a user's mailbox, but they all end up in one large file (i.e., a PST file for Exchange). So, retrieving an archived record can become a daunting task. Sponsored By: Page 3 of 10

4 The lifecycle of backup copies When we no longer need a backup copy of a file, usually because we have a sufficient number of point-in-time copies, we simply delete the oldest copy or backup job of which the file is part. This step is typically automated for us. Likewise, when we restore a file from a backup copy, we know what we are looking for and we may opt to select a point-in-time copy or version based on a date criteria. If long-term backups are used in lieu of archives, things can get a lot more complicated. Other than to satisfy a legal or regulatory compliance requirement, archives are used to free up primary (production) disk storage space from data that is no longer actively used but must be retained. Keeping an entire backup job for seven years as per our earlier example is not a very cost-effective way to use storage. Because backups only copy data, the original file is left in place, which frees up no space at all. In addition, the backup creates yet another copy of the data, which means we are now using twice as much storage space as before unless files are deleted manually after the backup. This only adds more data management overhead. Furthermore, because a lot of backups are organized in a sequence (i.e., full and incremental), a full backup has to potentially be taken out of sequence to capture the desired point-in-time full copy of a file. Day 3 of an incremental backup sequence would be useless without the previous full and incremental backups. Archives One way that archiving software is different from backup software is the cataloging and search capabilities. Metadata about archived objects is stored in a database and can be searched based on user-supplied criteria. Some backup software products also offer basic archiving capabilities where files can be archived, individually or in groups, and retained independently from the backups. Archived objects can be named or labeled based on the type of data, date, ownership or any other searchable criteria deemed appropriate to ease the search process for future reference. Sponsored By: Page 4 of 10

5 However, for organizations generating and handling large volumes of archives such as , imaging data, etc., the ability to create a simple searchable label is no longer sufficient. More sophisticated archive solutions providing search capabilities based on content, ownership, etc. are required. Just picture trying to find a 5-year-old patient record or court case transcript using your backup software's search wizard! Another challenge with archives that backup software simply can't handle is the static nature of aging archived data vs. the very dynamic technology used to access that same data. As much as software vendors try to maintain backward compatibility with some applications, data eventually ages to a point where it can no longer be easily or usefully accessed with the latest release of an application. Some sophisticated archive solutions have integrated conversion capabilities to allow future access to certain data using a more universal format. An example would be the conversion of reports to PDF format, which allows future access to those reports without requiring the application that created them. Archived files are typically maintained "as is" and are not alterable. So, an archive really isn't a backup copy kept for a long time. We can also add that using backup software to produce large amounts of archives that may eventually need to be searched (i.e., legal discovery) is a bad idea. Sponsored By: Page 5 of 10

6 Five IBM Tivoli Storage Manager backup errors and how to prevent them By Pierre Dorion What you will learn in this tip: Like most enterprise-class backup tools, IBM Tivoli Storage Manager (TSM) is flexible and customizable. However, care must be taken when configuring TSM to avoid inappropriate settings that could potentially make the backup environment difficult to manage and lead to errors. In this tip, learn about are five of the most common Tivoli Storage Manger backup errors and how to prevent them. Database backups and recovery log size One of the most common Tivoli Storage Manager backup errors is due to improper sizing of the recovery logs. During data backup operations, the TSM server writes backup transaction information to the recovery log and then commits it to the database. The recovery log is used to allow a failed database to be restored from its last backup, and all transactions recorded in the recovery log after the last database backup are applied to the recovered database to bring it to its latest state (known as roll-forward mode). As data backup activity takes place, the recovery log uses more space as it stores transaction information, and whenever the TSM database is backed up, the recovery log is flushed of all transaction information. If the recovery log reaches full capacity before the next database backup, the server will stop accepting new transactions; it will automatically be halted and cannot be restarted until the recovery log is extended manually. This is a common error that is usually caused by failed database backups (e.g., no scratch tapes available) and typically the result of poor activity monitoring. In earlier versions of TSM, the maximum size for the recovery log was 13 GB. This has been increased to 128 GB as of TSM version 6.1. While this increased log size allows more latitude, it must still be monitored to prevent the TSM server from unexpectedly halting, should that new log capacity be reached. The best way to prevent this situation is to ensure there are always enough scratch tapes for database backups and to monitor the database backup success and recovery log utilization. Sponsored By: Page 6 of 10

7 Undersized primary disk storage pools In environments where both disk and tapes are used as backup data storage targets, disk is frequently used as the primary storage pool where backup data is initially written (or staged) and later transferred (migrated) to a tape pool. A common error encountered in these environments is the undersizing of the primary disk pool, which can cause backup delays and even missed backup windows. When a disk pool fills up or reaches its high utilization threshold, it automatically starts migrating data to a designated tape pool. This can cause serious delays to the backup process, depending on the number of tape devices available and the number of concurrent backup sessions when the migration started. Hard drives are random-access devices and, therefore, a disk storage pool can support as many simultaneous backup sessions as the I/O capacity of the server will permit. However, TSM uses tape devices in a sequential manner and only allows a single data stream at a time between the disk pool and an individual tape device, and will allow multiple migration processes if multiple tape drives are available (one migration process per tape drive). If insufficient tape devices are available, backup sessions are queued and will use storage resources as they become available. In significantly undersized disk pool environments, this may cause some backup sessions to run beyond allowable windows or even fail. The best practice approach to prevent this type of situation is to size disk pools to hold as much backup data as will be directed to them during a backup window. In other words, if 700 GB of data is backed up daily and sent to a disk pool, this pool should be at least 700 GB in capacity. As an alternate method, large file backup clients such as database servers can be configured to bypass disk pools and backup directly to tape provided there are enough tape devices available to allow it. Inadequate tape check-out proecedures A properly configured TSM environment will have a scheduled process that copies all primary storage pool data to a copy pool, and performs a daily database backup to be be sent offsite for disaster recovery purposes. These tape volumes must be properly checked out of the tape library (ejected) and sent offsite. It's not uncommon to encounter Sponsored By: Page 7 of 10

8 environments where these tapes are checked out and sent offsite only once a week. This can lead to up to one week of data loss in the event of destructive events such as floods, tornadoes, hurricanes, fires, etc., depending on when the tapes where last sent to the vault. If company policies dictate that data must be backed up daily to meet a defined recovery point objective (e.g., 24 hours), then an offsite copy must be created daily and sent offsite daily. The situations described above can be easily circumvented with proper procedures and capacity planning. Tapes should be ejected from the library and sent offsite daily if an RPO of 24 hours is required. If handling tape media on a daily basis is not practical, then a remote replication solution (disk-based, VTL or TSM native) must be considered. With respect to tape library capacity, the device must be upgraded with enough capacity to hold the entire backup data set with room for growth. Alternatively, part of the data on tape could be migrated to a deduplication-capable disk-based solution and/or the data retention policy can be reduced. Expiration process The expiration process frees up storage pools space by marking files for deletion once they have reached a predefined retention period. It also frees the database of entries, which helps manage the size of the database. In larger TSM environments, the expiration process is sometimes not allowed to finish before it's interrupted. In fact, the TSM software allows administrators to set a duration parameter to limit how long this resource-intensive process will run daily. While the ability to interrupt the expiration process can be convenient, it can cause some other issues. If you don't allow the expiration process to finish, this can lead to more new database records being created than expired. This can negatively impact the size of the TSM database, and prevent the expiration process from ever catching up. There are many reasons why the expiration process can take longer than usual to complete, which can include the recent manual deletion of a significant amount or backup data, a resource constrained TSM server (CPU, memory, I/O), or a TSM database that has grown beyond a manageable size for a single TSM server instance. This situation can be prevented with proactive monitoring to address server performance issues before they seriously affect Sponsored By: Page 8 of 10

9 daily TSM processing. Avoiding the deletion of large amounts of data at once can help in already heavily utilized environments. In addition, deploying a second TSM server instance may be required in large environments. Maximum concurrent sessions Another common error involves the setting for the maximum number of allowable concurrent backup sessions, or the MAXSESSIONS TSM server option. This error is common in newly implemented TSM environments or in environments where a large number of new backup clients are added at once. The default number of allowed concurrent sessions is 25, which can be easily missed or exceeded. This condition, combined with a short backup start window (default is one hour) can cause backups to be missed. And, if this is allowed to go undetected, it can cause an exposure to data loss. As with many of the other errors outlined earlier, adequate and regular monitoring can easily detect this type of issue. That said, the best way to prevent this from occurring in the first place is to develop a check list of configuration items when adding new backup clients or making any other significant changes in your TSM environment. IBM TSM is a highly customizable and flexible backup product and, when properly implemented, it's an effective backup solution. That said, the product s flexibility also adds to its complexity, which sometimes leads to configuration and operational errors. As with any other backup software, the key to early error detection and correction is proper monitoring. Insufficient monitoring is by far the top error, but it's also the easiest one to prevent. Sponsored By: Page 9 of 10

10 Resources from IBM Worldwide Database Development and Management Tools 2009 Vendor and Segment Analysis Your Enterprise Data Archiving Strategy InfoSphere Optim Data Redaction About IBM At IBM, we strive to lead in the creation, development and manufacture of the industry's most advanced information technologies, including computer systems, software, networking systems, storage devices and microelectronics. We translate these advanced technologies into value for our customers through our professional solutions and services businesses worldwide. Sponsored By: Page 10 of 10