DISK- STORAGE UNITS – ASSESSING THE BENEFITS AND RISKS OF DISK-TO-DISK BACKUP B. Roth June 20, 2003

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

TABLE OF CONTENTS Overview ................................................................................................................................................... 3 What Problems Are We Trying to Solve?........................................................................................... 3 Product Introduction ................................................................................................................................. 3 StorageTek BladeStore B150 ............................................................................................................. 3 VERITAS NetBackup 4.5 .................................................................................................................... 3 NetBackup Architectural Overview ..................................................................................................... 4 Disk-to-Disk Backup & Restore Data Paths ....................................................................................... 6 Performance Characteristics.................................................................................................................... 7 High-Performance, Full-Volume Backup – Disk & Tape ................................................................... 8 High–Performance, Full-Volume Restore – Disk & Tape.................................................................. 8 Single-File & Subdirectory Restores – Disk & Tape .......................................................................... 9 Cost Considerations ............................................................................................................................... 10 Risks and Limitations.............................................................................................................................. 10 Retention Period - Scalability ............................................................................................................ 10 Portability............................................................................................................................................ 11 Hardware Failure ............................................................................................................................... 11 Process Failure .................................................................................................................................. 11 Potential Benefits.................................................................................................................................... 11 Solutions.................................................................................................................................................. 13 Decreasing the Backup Window....................................................................................................... 13 Reducing Restore Times................................................................................................................... 14 All Backups to Disk – Vault Some to Tape....................................................................................... 14 Remote Site Backups to Centrally Located Disk ............................................................................. 15 Conclusions............................................................................................................................................. 15 Augmenting Tape-Based Data Protection Solutions with Disk ....................................................... 15 Using NetBackup Vault to Create Backup Image Copies ............................................................... 16 Appendix A: Configuration Details......................................................................................................... 16

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Overview The introduction of reduced-cost ATA-based secondary disk-storage products is dramatically altering the way enterprises deploy mission-critical backup and archival environments. Specifically, low-cost disk-storage solutions are allowing enterprises to integrate disk-to-disk backups into their dataprotection systems that have relied solely on tape, in essence merging the speed and convenience of disk-based storage with the reliability and portability of traditional tape-based technologies. Still, many questions regarding the applicability of secondary disk-storage solutions remain unanswered. Does ATA’s low cost, for example, imply that the total cost of ownership for a disk-to-disk backup solution will be lower than a tape-based solution when all factors are considered? Should administrators perform all backups using disk-to-disk solutions, or should they target specific backup jobs with this methodology? And what problem or problems does this actually solve? What Problems Are We Trying to Solve? Deploying ATA-based secondary disk storage in a data-protection solution can resolve a variety of issues confronting backup administrators. These include shrinking backup windows, demanding restore time requirements, and the need to purchase additional tape drives or a new tape library. This white paper explores “When,” “How,” “Where,” and “Why” associated with deploying secondary disk storage for protecting business-critical data, examining many of the issues backup administrators face as they migrate from archival systems based exclusively on tape to those that add the benefits of disk drive technology. It begins by introducing two products – the StorageTek BladeStore B150 disk subsystem and the VERITAS NetBackup 4.5 archival software – and a three-tier architecture that facilitates deploying and managing the next generation of archival systems. This white paper also provides a variety of benchmarking performance statistics that can help backup administrators make better-informed decisions about merging disk-based storage with tape technology. Finally, this paper offers several possible scenarios for integrating disk-storage units into tape-based archival environments

Product Introduction StorageTek BladeStore B150 The StorageTek BladeStore B150 disk subsystem’s innovative Intelligent BladeStore Architecture allows storing large quantities of data in a small footprint at a greatly reduced cost. It combines low-cost ATA disk drives for data storage with the performance and reliability of an enterprise-class Fibre Channel disk system. This makes the BladeStore disk subsystem ideal for storing high-volume, fixedcontent data such as video, email, documents, or medical images online. It also offers excellent benefits for enterprises needing to rapidly back up and restore high-availability information, putting it at the heart of data-protection and business-continuity planning. StorageTek’s BladeStore disk subsystem takes emerging ATA-based disk-storage technologies a step further, delivering storage density advantages and the performance, flexibility, and manageability characteristics that customer with enterprise open systems environments demand. VERITAS NetBackup 4.5 VERITAS NetBackup DataCenter protects virtually every open systems operating environment, eliminating the need to manage complex data environments from multiple sites or with multiple tools. In addition, it simplifies operations such as database backup and recovery. For Global 1000 enterprises

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

looking to protect hundreds or even thousands of gigabytes of data, the highly scalable, three-tier architecture of NetBackup DataCenter provides fast, reliable backup and recovery of all types of data on any platform. Additional NetBackup product information is located at: http://www.veritas.com/products/category/ProductDetail.jhtml?productId=nbux&_requestid=27794 NetBackup Architectural Overview As illustrated in Diagram 1, the NetBackup software’s three-tier architecture consists of a NetBackup master server, NetBackup media servers, and NetBackup clients. In some configurations, the master and media server functions will coexist on the same physical platform. The master server manages backups, archives, and restores. Media servers provide additional storage by allowing the NetBackup software to use the storage devices they control. Media servers can also increase performance by distributing the network load.

Master Server(s)

Media Server(s)

Clients

Diagram 1: NetBackup Three-Tier Architecture

Disk-Storage Unit A NetBackup storage unit is a group of one or more storage devices attached to a NetBackup server. During a back-up or archival operation, NetBackup stores the backup data on the storage units set up during configuration. NetBackup 4.5 supports using disk storage as backup media. A disk-type storage unit consists of a directory on a hard disk that stores the backup or archive data. NetBackup software supports an unlimited number of disk-storage units.

Disk-to-Disk Backup The NetBackup software’s policies allow defining the rules followed when backing up clients. A subset of the policy attributes defines the destination policy storage unit. As stated earlier, the storage unit defines where NetBackup stores backup or archive data.

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

The destination policy storage unit can be specified in the following ways: •

Any Available - NetBackup tries locally attached storage units first, and, if none is found, it tries the remaining storage units in alphabetical order.

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A Specific Storage Unit - NetBackup uses a specific storage unit.

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A Storage Unit Group - NetBackup uses a prioritized list of storage units grouped together.

NetBackup policies can be configured with an automated wizard, through the administrative GUI, or via command line. These policies allow the backup administrator to use a specific disk or tape-storage unit, or a group of prioritized storage units, for a particular backup or archive operation. This level of granularity makes it possible to configure solutions that save backup or archive data based on the availability of storage unit resources.

NetBackup Vault Option Performing backups and archives to secondary disk storage offers key benefits to data-protection solutions while also introducing new risks and exposures. Among the risks and exposures are new potential failure conditions not commonly associated with traditional backup solutions. For instance, a catastrophic event that destroys the secondary disk-storage subsystem would leave existing backup images unavailable. In another example, a well-intentioned administrator could unknowingly allocate disk space associated with a disk-storage unit for other production data, overwriting existing backup images. Although these types of events are unlikely to occur, a properly designed data-protection solution includes safeguards that facilitate business continuity as well as disaster recovery. The key to enabling these safeguards is the ability to create duplicate copies of backup images on removable tape media. VERITAS NetBackup Vault fully automates the duplication of backup images through use of the NetBackup scheduler, which also includes offsite media tracking and reporting functions. The NetBackup Vault option, an integrated solution enabled by a license key, offers users intuitive GUIdriven tools that require no scripting or professional services for deployment, configuration, and general use. NetBackup Vault’s flexible duplication capabilities include: •

Inline Tape Copy – Creating up to four backup image copies simultaneously during the initial backup.

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Disk-Tape Staging – Copying up to four disk-to-disk backup images to tape simultaneously.

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Tape-Tape Copy – Creating up to four copies of tape-based backups simultaneously.

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Catalog Tracking – Tracking up to 10 copies of a backup image in the NetBackup catalog.

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Multiple Retention Periods – Assigning each of up to 10 copies of a backup image a unique retention period at backup creation.

Specific to disk-to-disk backups, NetBackup Vault is the ideal vehicle for duplicating and tracking of disk-based backup images to removable tape media. NetBackup Vault can also be configured to delete the original disk backup image based on user-supplied criteria. This technique can automatically free up secondary disk storage to accommodate new backups to disk.

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

NetBackup Vault permits straightforward deployment of strategies that incorporate duplicating backup images from secondary disk storage to create multiple copies of tape-based media. The software’s inline duplication feature allows creating up to four tape copies simultaneously. NetBackup software tracks the primary backup copy, which will be used to perform restores. When configuring duplicate operations, administrators can easily designate one of the copies as the primary copy. Customers looking to duplicate disk-based backup images to one set of tape-based media for onsite usage, a second set for disaster recovery, will appreciate this powerful option. Just as importantly, backup images migrated to tape with this methodology can be restored directly to clients, without performing a multi-step restore in which data is restored from tape to a disk-storage unit, then restored to the client. This has substantial impact: •

Images duplicated from disk to tape and restored directly to the client are restored faster.

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No secondary disk-storage space is required to restore data from tape.

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NetBackup automatically updates its internal catalog to track primary and non-primary copies of duplicated backup images as opposed to hardware-only solutions that simply duplicate tape or disk blocks.

Disk-to-Disk Backup & Restore Data Paths

Client NetBackup Master / Media Server L-180

LAN

SAN

Blade Store B150

Diagram 2: Backup Topology

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Diagrams 2 and 3 depict the data paths for NetBackup backup, image duplication, and restore processes. Backup: Data backed up or archived travels from the client to a NetBackup media server, where it is written to a disk-storage unit. NetBackup Vault then duplicates the disk-based backup images to removable tape media.

Client NetBackup Master / Media Server L-180

LAN

SAN

Blade Store B150

Diagram 3: Restore Topology Restore: NetBackup software retrieves client data from the disk-storage unit or tape media, then routes it through the NetBackup media server to the desired destination client. The NetBackup software’s internal catalog tracks the primary copy and any additional copies of the backup image. Restores are performed from the primary copy of the backup image.

Performance Characteristics This section provides lab-generated data that identifies the performance characteristics inherent in specific disk- and tape-based secondary storage products. Properly interpreted, these characteristics can give backup administrators an understanding of where they can deploy disk-to-disk backup solutions advantageously. Note: Hardware, software, configuration information, and test data used to generate the following performance characteristics are detailed in Appendix A of this document.

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Note: Sustainable data-transfer rates for products not characterized is likely to vary significantly from the products investigated in this study. High-Performance, Full-Volume Backup – Disk & Tape This test compares the elapsed time required to perform a full-volume backup from a high-performance primary disk subsystem through a high-bandwidth server to both secondary disk storage and tape media.

Test Description

Single-Stream Elapsed Time

Single-Stream ffective Data-Transfer Rate

Backup to BladeStore B150

215.76 s

46.32 MB/s

Backup to 9840A FC

671.20 s

14.89 MB/s

Table 1: Full-Volume Backup Comparison Test Analysis: •

Full-volume backups performed to the StorageTek BladeStore B150 disk subsystem executed in approximately one-third the time required for the same backup performed to a StorageTek 9840A FC tape drive.

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The data-transfer rate for BladeStore B150-based backups was approximately three times the data-transfer rate for the same backup to a 9840A FC tape drive.

This benchmark shows clearly that backups performed to a BladeStore B150 can reduce the backup window significantly. We did not perform benchmarks between the BladeStore B150 and higherperformance tape drives (such as the StorageTek 9840B FC). Nor were scaling characteristics derived. The ability to add additional tape drives to permit multistreaming backups was not compared with multi-stream backups to a BladeStore B150. We believe the BladeStore B150 can easily accommodate multiple simultaneous backups and/or restores without notable performance degradation. Note: We utilized NetBackup buffer tuning techniques to achieve the results shown in Table 1. Different configurations, including subject data to be backed up, may produce results that vary substantially from those in Table 1. High–Performance, Full-Volume Restore – Disk & Tape This test compares the elapsed time required to perform a full-volume restore from both secondary disk storage and tape media through a high-bandwidth server to a high-performance primary disk subsystem.

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Test Description

Single-Stream Elapsed Time

Single-Stream ffective Data-Transfer Rate

Restore from BladeStore B150

1152 s

8.70 MB/s

Restore from 9840A FC

717 s

13.98 MB/s

Table 2: Full-Volume Restore Comparison Test Analysis •

Full-volume restores from a StorageTek 9840A FC tape drive completed in approximately 62% of the time required for a restore from the StorageTek BladeStore B150.

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The data-transfer rate from a 9840A FC tape drive-based restore was approximately one-anda-half times the data-transfer rate for the same restore from a BladeStore B150.

The results suggest that performing a full-volume restore from tape is faster than the same full-volume restore from disk. Deploying the NetBackup Vault option to facilitate backup image duplication from disk to tape will allow customers to take full advantage of higher-performing full restores from tape. Single-File & Subdirectory Restores – Disk & Tape This series of tests compares the elapsed time required to perform non-sequential, random single-file and subdirectory restores from both secondary disk storage and tape media through a high-bandwidth server to a high-performance disk subsystem.

Test Description

Elapsed Time

Non-sequential Single-File Restore from BladeStore B150

11 s

Non-sequential Single-File Restore from 9840A FC

132 s

Non-sequential Subdirectory Restore from BladeStore B150

15 s

Non-sequential Subdirectory Restore from 9840A FC

140 s

Table 3: Single-File & Subdirectory Restore Comparison Test Analysis •

Non-sequential single-file and subdirectory restores performed from a StorageTek BladeStore B150 completed in substantially less time than the same restores performed from a StorageTek 9840A FC tape drive.

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

•

Restoring from the BladeStore B150 eliminates media cartridge movement, mount delay, and positioning.

The single-file tests restored the same 10 randomly selected files from both a BladeStore B150 and a 9840A FC. The subdirectory tests restored the same 10 randomly selected subdirectories from both a BladeStore B150 and a 9840A FC. We believe the performance advantage achieved when restoring from a BladeStore B150 would be even greater when restoring from a large backup image. The full-backup image used in this example consisted of 9.76 GB of data on a volume containing 10,000 1 MB files in 1,110 subdirectories. A larger backup image spanning tapes, for example, might have further delayed restores if some of the requested files or subdirectories resided on multiple tape cartridges.

Cost Considerations In some cases, the cost of removable tape media is lower than that of the equivalent quantity of secondary disk storage. Depending on how customers deploy disk storage, and the problems they are attempting to resolve, they may realize other cost savings from this strategy. •

A smaller number of tape drives may be required when used in conjunction with disk-storage units. Client backups are staged to disk-storage units during a shortened backup window and then duplicated with the NetBackup Vault option to tape in the background during normal production hours. Because client performance is not impacted, data duplications can run at a slower data-transfer rate. This strategy can also help delay the purchase of new tape drive technology or additional tape drives.

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Some customers may choose to Vault to tape only a subset of data backed up to disk-storage units. For instance, a particular client’s service level agreement may dictate that only weekly full backups are duplicated to tape and retained for an extended period. Daily incremental backups written to disk-storage units may not need to be duplicated, further reducing tape drive and removable-media costs.

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Remote- or branch-office data is often replicated to secondary disk storage at a disasterrecovery site, where it is then backed up and duplicated. The type of solutions described in this paper can eliminate using multiple small tape library units, resulting in substantial cost savings over time.

These examples represent only a subset of possible cost-saving scenarios associated with deploying disk-based secondary storage.

Risks and Limitations Retention Period - Scalability Secondary disk and tape storage subsystems can be scaled to retain a substantial quantity of data by adding the appropriate removable tape or disk media. Scaling tape subsystems may appear to be the less expensive option, but at some point the costs associated with increasing slot count or the cost of manually exchanging cartridges must be considered. The scaling of disk-storage units is limited by the maximum file system size supported by the NetBackup media server’s operating system. This limits the ability to scale a single disk-storage unit.

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Because NetBackup software supports an unlimited number of storage units, scaling can be accomplished by deploying new disk-storage units. A single StorageTek BladeStore B150 can be deployed as multiple disk-storage units attached to single or multiple NetBackup media servers. Sharing a single disk-storage unit between NetBackup media servers is not supported. Portability One of the clear advantages of removable tape media is that it is easily transported for offsite storage. An offsite, offline, tape-based copy of backup data is a key component of any comprehensive disasterrecovery plan. Replicating secondary disk storage backup images to a remote site with additional secondary disk storage offers intriguing business continuance value. Users implementing the disk-todisk strategies outlined in this paper should realize that they do not eliminate the need for offsite, offline tape media. Hardware Failure The StorageTek BladeStore B150 is an enterprise-class product, providing unsurpassed availability and reliability. VERITAS Software recommends using the NetBackup Vault option to duplicate all mission- and business-critical backup images written to disk-storage units and removable tape media. In the highly unlikely event of secondary disk-storage hardware failure, having one or more duplicate images of the backup or archive data on tape adequately protects customer data and facilitates ondemand restores. Process Failure Secondary disk storage adds another component, and another possible point of failure, to what may seem to be an overly complex data-protection solution. Although this factor must be considered, initial backups performed to secondary disk storage may actually remove complexity and points of failure inherent with tape-only solutions. For instance, backup or archive operations performed to secondary disk storage do not require allocation of tape cartridges or tape drives, robotic movement, media mounting, media positioning, media offline, or media eject operations. From this perspective, it is clear that performing backups to secondary disk storage can eliminate more points of failure than it introduces. Duplicating backup images from secondary disk to tape occurs in the background, independent of backup clients. Failures encountered in this mode may impact schedules used for offsite tape rotations but do not generally impact backups or archives from the client perspective. When compared to typical tape-duplication operations performed to create offsite disaster-recovery media, disk-to-tape duplication is less complex. It does not require a tape drive for read operations, and the disk-storage unit can perform simultaneous reads and writes, so the duplication process does not monopolize secondary disk resources.

Potential Benefits What, then, are the potential benefits to using secondary disk storage for data protection? Here are some of them: •

Backup to disk is faster than backup to tape.Benchmark data that substantiate these claims should be presented as evidence. Make sure results haven’t been skewed by the use of older, retired tape drives that do not match the performance available with current tape drive technologies. Also keep in mind that not all secondary disk-storage subsystems exhibit the performance characteristics of the StorageTek BladeStore B150.

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Backup to disk doesn’t require multiplexing backups from many slow clients onto a single tape. The benefit: tuning the multiplexing of multiple tapes for optimal performance is no longer required, and restoring from a multiplexed tape is no longer required. NetBackup software does not require nor support the ability to multiplex client backups when using a diskstorage unit. This benefit is believed to be 100% true in the case of NetBackup.

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Backup to disk eliminates the mount and positioning delays associated with tapebased backup and restores. The benefit: eliminating mount and position delays. These delays typically last from a few seconds to a few minutes, depending on the type of tape technology deployed and other factors. This benefit occurs when using disk-storage units such as the StorageTek BladeStore B150 that do not emulate physical tape devices. We believe that the cumulative effect of performing many backups and restores to disk-storage units could result in substantial time savings.

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Creating duplicate copies of backup images from a disk-storage unit to tape can be performed as an offline operation, independent of the original client that was backed up. The benefit: creating duplicate backups is simple, with no additional impact on the client. This is believed to be 100% correct in cases where the original client and media server reside on separate platforms. NetBackup Vault enables automated duplication of backup images from disk-storage units to tape. Users are not forced to use, modify, or manipulate scripts. NetBackup Vault allows creating up to four simultaneous copies on the same destination media server, with each copy supporting different retention periods, if desired. NetBackup can track up to 10 copies of a particular backup image.

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Restoring from a disk-storage unit does not require an available tape drive. Assuming that the disk-storage unit has the capacity to maintain backed up data for a reasonable retention period, and that the data to be restored exists on a disk-storage unit, the restore could be performed without a tape drive. Many data-protection solutions designate one tape drive within a given storage subsystem as a restore-only unit that is never used for backups. The properly designed and deployed disk-storage unit solution eliminates the need for maintaining this restore-only tape drive in many cases.

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Backups, restores, and duplication operations can be performed simultaneously with a disk-storage unit. NetBackup software can perform up to a maximum of 256 concurrent jobs with each disk-storage unit. It places no limitation with regard to executing simultaneous backup, restore, or duplication jobs, as long as the maximum number of concurrent jobs is not exceeded.

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Backups and restores using disk are likely to be less failure prone. The expectation of more reliable backups and restores can now be achieved. Although there is no analytical data available to substantiate this claim, backups to disk and restores from disk eliminate the mechanical operations inherent in tape-only solutions.

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Restores from images resident on disk-storage units are performed without taperelated operational overhead. Disk-storage units are available to perform restore operations simultaneously with any backup, archive, or duplication operations that may be executing. This eliminates the need to have an idle tape drive available for restores, reducing complexity and the potential for failure. Restores from images duplicated to tape media and expired on diskstorage units occur as any normal tape-based restore would. This eliminates the need to first restore to the disk-storage unit, then restore to the client. Restores from tape media are written directly to the desired destination client without additional overhead or resource requirements.

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•

Creating offsite disaster-recovery media from disk-storage-based backup images is simpler than creating the same media from tape-based images. The rationale for this claim -- that creating offsite disaster-recovery media from disk-storage unit-based backup images is simpler than creating the same media from tape-based images – is the fact that a restore-only tape drive is not required. Furthermore, some customers do not duplicate all images to media intended for offsite safekeeping. In this case, multiple pieces of tape media may need to be mounted and positioned to create a single collection of offsite tape media. Disk-storage unit images can be read without the mounting and positioning overhead associated with tapes.

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Speed – Where is the Real Advantage? The known performance characteristics of the StorageTek BladeStore B150 show it clearly demonstrates the ability to perform high-speed backups as well as high-speed, non-sequential single-file and subdirectory restores in conjunction with VERITAS NetBackup. The BladeStore B150 can be connected directly to NetBackup media servers via Fibre Channel point-to-point or SAN topologies.

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Ability to Restore - Confidence Factor. A properly designed and implemented dataprotection solution that combines the advantages of both tape and secondary disk storage may exhibit a higher probability of restore success. Using NetBackup Vault to automatically duplicate backup images allows restoring from up to 10 backup images. In the highly unlikely event of a secondary disk-storage failure, customers that have duplicated backup images to tape can simply choose to either expire the disk-based image or change the primary copy designation within NetBackup and perform the restore operation from tape.

Solutions Without question, teaming the StorageTek BladeStore B150 with VERITAS NetBackup 4.5 software opens the door to a wide variety of potentially advantageous data-protection solutions. This section explores several potential data-protection scenarios that can deliver specific tangible business benefits to customers with enterprise open systems environments. Decreasing the Backup Window This solution, designed to decrease the backup window, utilizes secondary disk storage as a buffer or cache that sits between the source clients and destination tape devices. In this scenario, our hypothetical customer relies on a limited quantity of older generation tape drives. The volume of client data has increased to the point where full backups cannot be completed within an agreed-to backup window dictated by the service level agreement in place. Limitation or Problem Full backups exceed the agreed-to backup window, with backups staggered so subsets of servers are backed up on different days, spreading the workload out across the week. Backups sometimes impact critical servers during peak production hours. For two key reasons, a failed backup attempt cannot be re-initiated until the following week: first the backup window would be exceeded; second, heavily utilized tape drives are required for other full backups on other days. There is also a serious risk of missing additional backups should the need to perform a full-volume or full-server restore occur. Enhanced Solution - Benefits Deploying a BladeStore B150 configured as a disk-storage unit allows completing full backups well within the prescribed backup window. Backups no longer compete with production workload on critical servers. Although no failures have occurred, we believe that a failed backup attempt could be retried

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and successfully completed well within the backup window dictated by the service level agreement. During production hours, disk-based backup images are duplicated to tape with NetBackup Vault, with no impact on client platforms. If a large restore is required, it is possible that data could be restored from the disk-based image, with minimal impact to other backups or duplications in progress, because disk-storage units can support simultaneous backup and restore operations. When a restore from tape is required, it would not impact duplication jobs in progress because tape drive utilization has been reduced to an acceptable level. Reducing Restore Times Our second sample solution, intended to reduce restore times, uses secondary disk storage as a repository for backup data, implemented with sufficient capacity to store backup images for an average of 30 days. Our imaginary customer has deployed new servers with a service level agreement requiring near instantaneous single-file and subdirectory restores of data backed up within the last month. Limitation or Problem Analysis work performed by the administrative staff determined that 90% of user restore requests involve retrieving data backed up within the last 30 days. In this scenario, typical single-file and subdirectory restores take an average of 15 minutes to complete. This time includes waiting for an available tape drive resource, mount and positioning delays, and the actual restoration of data. Nonsequential restore requests can consume significantly more time, when specific files residing on widely separate portions of the tape media require additional positioning delays or, in some cases, mounting of different media altogether. Enhanced Solution - Benefits The hypothetical customer deployed multiple BladeStore B150 storage systems to augment its existing data-protection solution. In this scenario, client data is backed up to a disk-storage unit residing on one of the BladeStore B150 unit and given a 30-day retention period . The disk-based backup images are duplicated to tape in the background with NetBackup Vault, with zero client impact. A 12-month retention period is set per the customer’s service level agreement for all tape-based images. Subsequently, 90% of client restore requests are completed within one minute after initiation. Restores of data that fall outside of the 30-day window are performed from tape directly to the destination client, bypassing the disk-storage unit. All Backups to Disk – Vault Some to Tape Our third sample solution, designed to mix tape and disk technologies, uses secondary disk storage as a destination backup device for all data. Based on dictated service level agreements, a subset of this data is also duplicated to removable tape-based media. Limitation or Problem This hypothetical customer has escalating storage requirements, while at the same time it has determined that some of the data it currently writes to tape is retained for only 30 days. As dataprotection requirements increase, the customer understands that it can add more tape drive and cartridge resources or deploy a BladeStore B150 to augment its existing data-protection infrastructure. Enhanced Solution - Benefits After this customer installed and deployed a BladeStore B150, all of its backups are performed directly to disk-storage units. All backup images that require more than 30-day retention periods are duplicated

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to tape media and assigned the proper retention status. Although the customer had already deployed new tape drive technology, it noted that backups performed slightly faster in this scenario because it eliminates mount and positioning delays associated with tape-based backup. The customer also noted improved non-sequential restore performance for images residing on disk-storage units. Longer term, the customer expects to spend slightly less on removable tape media. The customer also believes the combined disk/tape solution to be more scalable over time, which may result in additional long-term savings. The customer noted a possible data-protection exposure with data retained for only 30 days and never written to tape. It installed VERITAS Volume Manager software, which allows easily mirroring of the secondary disk storage attached to the media server, providing a higher degree of availability in the process. Remote Site Backups to Centrally Located Disk The fourth example solution, designed to eliminate remotely located small tape libraries and their associated costs, demonstrates the ability to back up remote clients with centrally located secondary disk storage. Limitation or Problem This would-be customer’s existing data-protection solution includes one relatively large central site and two small remote sites. The customer expects to add more remote sites to the configuration, and is thus looking for ways to reduce the costs associated with protecting data at the remote sites. These costs consist of manually administering the remote tape libraries, daily cartridge inject and eject workload, plus the cost of purchasing and maintaining the remote libraries. The customer tried to get the local office staff to assist by having them volunteer to add and remove tape cartridges; however, this task was often overlooked, and tape media was often unavailable for backups. The administrative staff considered this a high price to pay, based on the estimated cost to re-create data left unprotected by mismanaged cartridges at the remote libraries. Enhanced Solution - Benefits By adding a BladeStore B150 at the central site the customer now backs up the remote sites to diskstorage units over the wire. Backups to disk from the remote sites are duplicated to tape with the NetBackup Vault option. The central site has also been enhanced with disaster-recovery capabilities, allowing it to act as a disaster-recovery repository for the remote sites. Small single-file or subdirectory restores still require the data to flow from the central site to the remote site. A full-volume or platform restore would be handled by restoring to a local machine acting as the disaster-recovery platform. The customer has saved significantly from this scenario, and also believes that it has a superior remote-site disaster-recovery solution in place.

Conclusions The BladeStore B150 is a high-performance secondary disk subsystem that can be configured in conjunction with NetBackup software, the NetBackup Vault option, and tape-based data protection solutions to create tangible, measurable business benefits in a wide range of customer applications. Augmenting Tape-Based Data Protection Solutions with Disk Both StorageTek and VERITAS take the position that all mission- and business-critical data should be protected with regular backups written to removable tape media. Ideally, this data should be stored on both local removable tape media as well as on remotely stored removable tape media. Tape-based solutions can easily be enhanced by incorporating disk-based secondary storage. Augmented solutions

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such as the ones described in this document can provide distinct benefits, including performance enhancements, increased data-protection capabilities, and potential cost savings. Using NetBackup Vault to Create Backup Image Copies Duplicating backup images to provide both basic data protection and offsite removable media storage for disaster recovery is a strategic business requirement. The NetBackup Vault option, enabled via a simple license key upgrade, is fully integrated into NetBackup 4.5 software. The GUI-driven configuration facility is designed to be an intuitive, easy-to-use tool.

Appendix A: Configuration Details This section lists the hardware, software, configuration information, and test data used to generate basic BladeStore B150 performance characteristics when used in conjunction with NetBackup software. Hardware: •

The NetBackup master server, media server, and client functions were hosted on a Dell PowerEdge 4600 platform with 4 x 2.20 GHz CPUs, 3,997,168KB RAM, and 4 JNI HBAs.

•

Brocade 3800 Fibre Channel switch

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StorageTek L180 Library containing two 9840A FC tape drives, f/w rev = 1.30

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StorageTek 9176 primary disk-storage subsystem

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StorageTek BladeStore B150

Software: •

Microsoft Windows 2000 Server, SP3

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VERITAS NetBackup 4.5, MP1

Test Data: •

A single 1MB file was replicated for a total of 10,000 files in 1,110 folders equaling 9.76 GB

•

Approximate compressibility of the test data was 2:1

Topology: •

Diagram 4 is a simple rendering of the Fibre Channel topology interconnecting the CPU, primary and secondary disk storage, and tape library resources.

•

The CPU Fibre Channel connections included zones for connection to each of two 9176 controllers, two B150 controllers, and a single zone for tape and robotic control within the L180 library.

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

StorageTek 9176 Disk Array

Dell 4600 W2K

Brocade 3800

StorageTek BladeStore B150

StorageTek L180 Tape Library

Diagram 4: Connection Topology

StorageTek BladeStore B150: •

The B150 was equipped with a single drive tray

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Drive tray 0 was subdivided into two logical volume groups, volume group 1 and volume group 2

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Each logical volume group was configured as a RAID 5 disk array

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Volume group 1 used physical blades 0, 1, 2, 3, and 5

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Volume group2 used physical blades 4, 6, 7, 8, and 9

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Each of the two volume groups was subdivided into four logical disks

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Two logical disks from each volume group were made available to the Windows 2000 Server as local drives

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Of the four logical disks, two were presented to the Windows 2000 Server via B150 controller A, and two were presented to the Windows 2000 Server via B150 controller B

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Disk- Storage Units – Assessing the Benefits and Risks of Disk-to-Disk Backup

•

Only a single logical disk was used to obtain the performance metrics contained in this investigation

Volume Group 1 Volume Group 2

0

0

0

0

1

0

1

1

1

1

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2

2

3

2

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3

3

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X

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0

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Physical Blade Number

Diagram 5: B150 Blades, Volume Groups, and Logical Volumes

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VERITAS Software Corporation Corporate Headquarters 350 Ellis Street Mountain View, CA 94043 650-527-8000 or 866-837-4827

For additional information about VERITAS Software, its products, VERITAS Architect Network, or the location of an office near you, please call our corporate headquarters or visit our Web site at www.veritas.com.

Copyright (c) 2003 VERITAS Software Corporation. All rights reserved. VERITAS, the VERITAS Logo, NetBackup and all other VERITAS product names and slogans are trademarks or registered trademarks of VERITAS Software Corporation. VERITAS, the VERITAS Logo, and NetBackup Reg. U.S. Pat. & Tm. Off. Other product names and/or slogans mentioned herein may be trademarks or registered trademarks of their respective companies.