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January 04, 2019

Fine-tune: Validating interleaved backups

DLT cartridge

Experts on 3000 practices are advising customers to get away from using tape devices. You may have no other choice while tending to an achival system, though. An interleaved backup requires special handling.

Backup errors on STORE tapes can occur when you try to restore on the exact same drive the backup tape was made on. There's a tape restore issue to manage with interleaved DLT tapes. For example, a DLT7000 must be on a different device adapter if tapes are to be used at the same time when backing up in interleave option. Interleaving provides a higher disk data rate. It is accomplished by reading from several disk drives (files) simultaneously. The file data is blocked together and then stored to the specified devices. The effect is to accelerate the STORE process.

The workarounds are to not use tapes on same device adapter for interleave restores, or put the DLT7000 devices on different device adapters.

It's not recommended to validate any tape after writing a backup onto it. "You always want to validate on a different different tape drive,” says Allegro's Stan Sieler. For example, on Intuit’s HP 3000s, “they happily validated the tapes for months. Then the tape drive was replaced, and no backups would validate on the new drive—or on any other drive.”

Finally, verifying a backup with validation can be done automatically right after the backup overnight, if you put the tape drive back online with the ONLINE utility. You can download ONLINE from Allegro’s website. 

10:55 PM | Permalink

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Comments

Comments

...isn’t putting the tape(s) back online to validate then a violation of the “Validate on a different drive than written” rule?

Posted by: Brian Edminster | Jan 12, 2019 4:38:20 PM

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