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Wilfred van Dijk avatar image
Wilfred van Dijk asked

Backup Log with checksum useful?

It seems you can use the Backup log command "with checksum", but I was wondering if this is useful. If I read the documentation, checksums are on data pages. Are checksums also on logfiles? If not, checksum seems to be useless on a logbackup
backup-restorelog-backup
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Thanks! Especially KB 189055 gives the answer on my question. The BOL was indeed a little confusing about using CHECKSUMS.
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You sure that is the right KB number? That number references a KB article on Excel 98.
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http://msdn.microsoft.com/en-us/library/ms189055.aspx is the article I mentioned (which is not a KB article)
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Grant Fritchey avatar image
Grant Fritchey answered
The checksum on the log backup will validate that it wrote to disk correctly, so yes, it can be useful as part of a thoroughly paranoid backup strategy. All part of [validating backups][1]. [1]: http://www.simple-talk.com/sql/backup-and-recovery/backup-verification-tips-for-database-backup-testing/
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Interesting that they don't show the command on the RESTORE article: http://msdn.microsoft.com/en-us/library/ms186858.aspx. But it speaks of using the command here: http://msdn.microsoft.com/en-us/library/ms189055.aspx. Ah, BOL contradictions are fun to find.
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And you've just started your own Howlers article. Submit it to the editors at Simple-Talk when you're done.
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Is BOL a little misleading in that the way it reads just RESTORE VERIFYONLY will check the CHECKSUM, but I thought you actually had to specify it (BACKUP VERIFYONLY FROM DISK=N'Myfile.bak' WITH CHECKSUM)?
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I'm pretty sure VERIFY ONLY will use the checksum automatically, if it exists. At least, that's my understanding of how it works. I think the RESTORE ... WITH CHECKSUM is something you do with a full RESTORE operation, use the CHECKSUM to validate the data as it reads it (and that's something I should have added to the article... nuts). I don't think it's needed with VERIFYONLY.
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