Storage Migration Products and Backup

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Disk-Based Storage Units

What's the best way to increase performance of your tape backup solution? Take the tape out of your backup and replace it with disk. Disk-based backup methods are becoming quite popular, with the cost of disks dropping dramatically in recent years. Before we get into the implementations of the disk-based methods, let's look at some of what is on the market today. First are disk-based solutions like Quantum DX-30 and Alacritus Software's Securitus Disk-Based Virtual Tape Library Appliance that frontend the disk to the backup software with what looks like a tape library. Then there are the filer-based solutions like Maxtor's MaxAttach, Network Appliance's NearStore, and even LeftHand Network's solution. Large independent software vendors (ISVs) like Legato and VERITAS offer diskbased backup solutions within their applications, as does one of the smaller ISVs, BakBone Software's NetVault. Like IBM's Tivoli Storage Management (TSM), they can use disks as a cache area during backup to stream the tape drives on the back end. At this point, you might be saying, 'But disks are a finite storage device.' That is true, so in order to implement a solution like this, you need to do some planning and maybe even some scripting, depending on the backup tool you have selected. We will use VERITAS NetBackup for any specific examples, but we believe the concepts can carry over to any other solution that supports disk-based backup.

Implementing Disk-Based Storage

Since disk-based storage is finite, you really need to take into consideration how you will manage it once your backups are on this device. More importantly, you need to determine which clients you want to back up to it. You surely cannot select all of the clients. That would require an equal amount of disk-based backup storage as online storage. So, practically speaking, it is best to determine ahead of time which clients you will be backing up to the device.

Once you have decided which clients will be backed up to the disk-based storage device, you need to do some math to figure out how long you can keep the backup images stored there. It is best to keep the backup there as long as you possibly can to facilitate faster restores should the need arise. For illustration purposes, let's say that you only have enough space for 72 hours before you will effectively run out of space. Now what? Well, you can migrate them manually by doing a copy, or duplication to a tape device. You can also implement a hierarchical storage management (HSM) solution, like VERITAS Storage Migrator, that will manage the filesystem for you automatically by migrating the 'data' to a secondary or tertiary storage device. Or you could use the plug-in module Watermark for Duplication Suite by Gray House Solutions, which will monitor the filesystem of the disk storage unit for growth and make a duplicate of the stored images on tape when the user-definable watermark is met, or it will expire backup images that already have more than one copy, freeing up valuable disk space. Another solution is to use NetBackup Vault to duplicate stored images through disk staging. Disk staging allows you to back up to disk and then schedule a duplication of the disk-based image to one or more tapes. The tape or tapes can have different retention periods both from the disk-based image and each other. You can also configure Vault to delete the disk image as soon as the duplication process successfully finishes.

The bottom line is that disk-based storage devices are inexpensive, fast, and typically highly reliable. The first rule of thumb when performance tuning is to address all of your bottlenecks-and tape may be one of those in your environment.



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Implementing Backup and Recovery(c) The Readiness Guide for the Enterprise
Implementing Backup and Recovery: The Readiness Guide for the Enterprise
ISBN: 0471227145
EAN: 2147483647
Year: 2005
Pages: 176

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