Summary

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Storage Migration Products and Backup

Full backups must by definition back up all the files within a filesystem. By adding an HSM software package such as VERITAS Storage Migrator to your NetBackup environment, you can drastically reduce the amount of data that needs to be backed up while still protecting all your data.

HSM manages filesystems for both optimizing space and reducing the management time. Optimizing space involves copying inactive files from the primary storage medium (hard drive) to another medium, like tape, optical, or a less expensive disk drive. Once the inactive data is secured within another medium, the data blocks on the primary don't need to be backed up anymore to safeguard the data.

An intelligent backup product like NetBackup recognizes that the HSM has safeguarded at least one copy of the data to another medium, so NetBackup only needs to back up the meta data (inode or placeholder information) for that file. So instead of backing up all the data blocks for all the static files in a filesystem during a full backup, it only needs to back up the active (nonmigrated) data and the placeholders for the migrated data. Real-world testing has shown that a backup of 3.5 hours can be reduced to about an hour by simply adding an HSM to your environment.

The primary reason that backups are ever done is for insurance; you need to be able to recover your company's data if, for some reason, it's gone. For the most part, you generally do backups in a leisurely manner (relatively speaking), but you almost always restore in a panic. Since using HSM technology can help speed up your backups by reducing the amount of data backed up, it can also increase your speed when restoring a filesystem. By doing your backups more intelligently by incorporating an HSM, you can not only decrease your backup window, but also your recovery window. With NetBackup and Storage Migrator, a full restore of a filesystem works exactly the same as a 'normal' restore, except that you only physically restore the 'active' nonmigrated files and all the placeholders for migrated files. All of the migrated files are readily available; just access the placeholders like any normal file, and Storage Migrator will cache the data blocks back to the filesystem, all automatically. Meanwhile, you're back in business, since your active data is back. You can start processing data faster than if you had to wait for all the active and inactive files to be restored. For safeguarding your data, it's highly recommended that you let the HSM make two copies of all your migrated data and that your second copy be taken off-site, along with your full and incremental tapes. This provides a disaster recovery set of tapes should you ever need them.

Starting with NetBackup 3.4 for UNIX, there is a tool called the File System Analyzer that analyzes a filesystem and reports back the usage patterns, size, and number of files within a filesystem. It provides a what-if scenario that you can change to see how many files you back up on every full backup that haven't changed in a long time. Most customers are very surprised at how much of their data isn't used very often. The analyzer can be very helpful in determining if a particular system or particular filesystem/volume within a system is a good candidate for an HSM product.

Another way you can utilize Storage Migrator with NetBackup is as a repository for backup images. It is not uncommon to have slow clients, and even with multiplexing, you can't always keep a tape drive streaming. Once a tape drive can't be kept streaming, the tape drive's performance is greatly reduced. A way to address this problem is to back up to a disk storage unit. Storage Migrator can then manage the disk storage unit. As NetBackup backs up these slow systems (or fast systems on slow networks), it creates backup image fragments. These fragments together are one NetBackup image. Storage Migrator then can migrate these fragments to secondary storage. By doing this, each client is creating its own backup images at whatever its speed without having a tape drive shoe-shining its tape head (shoe-shining, as we discuss in Chapter 9, means that the drive is not streaming and must wait to receive data then reposition the tape before writing continues). Once the backups are done, Storage Migrator can efficiently copy the images to tape. Now, as most system administrators know, most restores are done within a few days of the backup. If you have adequate disk space, the images could still be on disk. Your restores would then be from disk instead of tape. If the image had been purged (the data blocks freed from disk for disk space considerations), when the restore accesses the placeholder, Storage Migrator will automatically retrieve the backup images from tape and the backup will continue as normal.



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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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