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Disk-based backup: how software vendors are adapting

With disk-based backup playing a growing role in the data center, the three major enterprise backup programs -- from EMC IBM and Symantec -- are undergoing radical changes.

This feature, focusing on the top three enterprise backup programs, first appeared in the April issue of Storage magazine.

With disk-based backup playing a growing role in the data center, the three major enterprise backup programs -- from EMC IBM and Symantec -- are undergoing radical changes.

As disk rapidly becomes the preferred initial backup target, vendors of the three big backup programs -- EMC Corp.'s NetWorker, IBM Corp.'s Tivoli Storage Manager (TSM) and Symantec Corp.'s Veritas NetBackup -- are scrambling to enhance and change the focus of their programs. Never before has a shift of such titanic proportions affected the product development of these three dominant players which, until now, have been slow to change.

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Of course, the most widely used backup software products have always provided some disk support, but vendors recognize the need for significant product upgrades to take advantage of disk's lower costs and unique restore capabilities (see Product roadmaps below). EMC's forthcoming NetWorker PowerSnap RecoverPoint module enables central management of EMC's continuous data protection (CDP) product; IBM's TSM advanced copy services for Exchange allows users to tap into Microsoft's Volume Shadow Copy Service (VSS) in Microsoft Exchange environments; while NetBackup's new PureDisk technology adds single-instance storage for remote-office protection (see Noteworthy new features below).

There's no question there will be some major bumps in the road for users as the movement from tape to disk-based backup accelerates. And they'll have reason to be wary. Some Symantec NetBackup users have been reluctant to upgrade to Version 6.0 because of the major code revisions. EMC's acquisition of Legato led it to provide more snapshot integration with EMC's storage product lines, but left existing NetWorker users with heterogeneous storage environments out in the cold. And IBM is showing little evidence it will support other vendors' disk storage products.

For example, Steve Shim, director of technical services at Health First, Rockledge, FL, was forced to look beyond IBM's TSM because he found its 24-hour recovery time unacceptable.

And it took three weeks for Arun Sondhi, the storage management group lead at a Milwaukee manufacturer, to integrate NetWorker with Sun Microsystems Inc.'s StorageTek ACSLS Manager. Backing up his servers behind a corporate firewall required the purchase of another NetWorker server because opening 25,000 TCP/IP ports on the firewall posed a huge security risk to the organization. His "reliance on backup software has become so big that if it sneezes, the CIO hears it," says Sondhi.

In response to user requests for new features, EMC, IBM and Symantec are:

  • Increasing their support for faster backups and recoveries
  • Enhancing support for encrypted data
  • Offering better ways to protect remote offices

Disk-based backup
Backing up to disk dramatically improves backup times, usually in the 30% to 50% range or greater. Aaron Mathes, chief operations officer for information services at Liberty University in Lynchburg, VA, finds that disk-based backup provides him with a higher degree of confidence that his backups are completing successfully. "Disk has had an exponential impact," he says, adding that he backs up 90% of Liberty University's 4TB of data to a disk cache.

The EMC, IBM and Symantec products all include the ability to manage a disk cache (it's an optional feature for NetWorker), a disk volume where data is initially parked before being moved to tape. Disk caches can be shared drives on an Ethernet network or a Fibre Channel (FC) SAN drive owned by the backup server. When using a disk cache it's important to:

Product roadmaps

EMC Corp. NetWorker: NetWorker 7.4, to be released within the next year, will include the following new features:

-NetWorker will manage all TCP/IP ports opened through a firewall. These ports will be locked and controlled by NetWorker to prevent other programs from using these ports and compromising the firewall.

-The PowerSnap module for the EMC RecoverPoint continuous data protection product will be released in April.

-Over the next year or two, all of the different NetWorker modules will be able to be managed from a central console.

Symantec Corp. Veritas NetBackup: The NetBackup 6.5 release is planned for the second half of this year. Some features Symantec plans to include or enhance are:

-Enhanced support for virtual tape libraries.

-A new shared disk option that allows SAN-attached disk volumes controlled by the master server to be assigned to client servers, which is similar to how Symantec's shared tape option now works.

-Improve the ability to restore from file-system snapshots so that only a single file is restored rather than the entire file-system snapshot.

-Integrate the PureDisk data de-duplication technology into NetBackup.

-Over the next year or two, integrate the data classification engine in Veritas Enterprise Vault with NetBackup to allow users to classify and categorize data on new backups, as well as classify data on old backups.

IBM Corp. Tivoli Storage Manager: Declined to provide information about the upcoming features it plans to offer in the next year or two.

  • Select volumes large enough for each server to keep a week's to a month's worth of backups online to expedite recoveries. NetWorker 7.3 has a wizard that assesses the size of each server's backup and required retention period, and helps administrators select a disk volume large enough to meet those requirements.
  • Determine what copies of the disk backup need to be written to tape and when. For instance, if a server does incremental daily backups and full weekly backups to the disk cache, you may opt to copy only the full weekly backups to tape to conserve tape and schedule the copies during low-traffic backup times to lessen their impact.
  • Use a watermark, which deletes or transfers backups from the disk cache when a certain level is reached, for example, 90% of disk capacity.

There are three basic ways -- high watermarks, time based and manual -- in which vendors allow users to manage disk cache threshold levels, although each feature is not in every program. "Sometimes you will want to force a migration from disk to tape," says Mickey Baker, a storage consultant at Safe Data Services LLC in Fort Lauderdale, FL. "But in TSM 5.2, there is no manual option [to do so]. You must wait until the buffer [disk cache] is full before a migration from disk to tape occurs."

Another major way traditional backup programs are changing is in their support for virtual tape libraries (VTLs). A VTL presents its disks as virtual tapes, and its disk array FC or iSCSI ports as virtual SAIT, SDLT or LTO tape drive images to the backup software. VTLs are easier to implement in the sense that backup software treats VTLs like physical tape libraries -- it will detect and manage virtual tapes and tape ports the same way it does with tape libraries. But users may pay extra for VTLs; they cost more on a per-megabyte basis than similarly configured generic disk arrays, and EMC and Symantec charge an additional software license fee to manage VTLs.

Backup software vendors license their VTL software by virtual tape ports or VTL capacity. Symantec initially licensed NetBackup for VTLs the same way it did for a tape drive -- by each virtual tape drive. Because a company may use tens -- if not hundreds -- of virtual tape drives, this licensing approach quickly becomes cost prohibitive. For instance, using Symantec's old model, licensing for 12 virtual tape drives on a 20TB VTL cost $60,000. Symantec now offers NetBackup licensing based on total VTL storage capacity. With the new model, the licensing cost for the 20TB VTL is only $20,000 ($1,000 per VTL terabyte); however, users still need to monitor VTL capacity growth to control future costs.

In addition to having to adjust to different licensing costs, some VTL users are finding that their backup bottlenecks are moving from the tape device to the server. As the speed of backups increase, the VTL puts more demands on the server to ship data to it faster. Ian McLeavy, manager of global enterprise storage at Black & Decker in Baltimore, implemented five EMC VTLs that lowered his NetWorker backup times from 11 hours to seven hours. But because of the increased CPU activity, says McLeavy, "the backup bottleneck has moved to the server."

Instant backup and restore
An offshoot of the growth of disk-based backup is the increased interest in backup and recovery technologies such as CDP and snapshots. NetWorker and TSM offer snapshot and replication options that support primarily array and virtualization technologies sold by their respective companies. TSM lets users execute instant restores and backups using IBM's TotalStorage DS6000 and DS8000 storage arrays or SAN Volume Controller (SVC). Similarly, EMC's NetWorker PowerSnap modules integrate predominantly with EMC's Symmetrix and Clariion storage arrays. Prior to EMC's acquisition of Legato, NetWorker offered PowerSnap modules that supported older IBM and Sun storage array models; going forward, the PowerSnap modules won't be upgraded to support non-EMC storage arrays.

With NetBackup 6.0, Symantec introduced Advanced Client, which allows the central management console to identify the host-, network- or array-based snapshot options available to the client server. It also grants the storage administrator the ability to remotely configure snapshots on that server.

But don't assume a backup program containing a wizard-like snapshot option will work out of the box. There are a number of tasks required to get some wizards to work in complicated storage environments.

For instance, NetWorker PowerSnap modules are licensed by specific storage devices, so a future storage array change requires changing the host software and licensing. If you're using a Clariion, you must first verify that it has up-to-date firmware; because Clariion supports two snapshot methods, you must then choose the type of snapshot to use -- copy on write or split mirror. The next step is to verify that the Clariion contains sufficient storage space for the desired type of snapshot. Finally, you must install EMC's Navisphere Host Agent, Navisphere CLI, PowerPath and NetWorker client software on the host before a snapshot is created. While these steps vary in complexity according to the backup software product, both TSM's and NetBackup's snapshot modules require similar steps.

McLeavy decided not to use snapshot modules. Instead, McLeavy scripts snapshots using SYMCLI commands because NetWorker didn't offer a PowerSnap module for the Tru64 operating systems he used at the time. While McLeavy is now moving from Tru64 to AIX, he still has no plans to purchase the PowerSnap Symmetrix modules because "the modules are a little pricey, considering we already have a working configuration."

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