September 22, 2010 at 7:33 am
My question is directly related to an editorial by Steve Jones on 9/20/2010, where he says that a 7TB database is small. We have a few databases in our organization that have geographic (mapping) data in them that are around 1TB each. We have a small business class computer system running them, 2 to 4 cores Intel based running windows server OS with a RAID HDD system. We recently had a problem that we had to run a dbcc checkdb on the larger of the 2 twice in a row to fix. This took more than 4 hours to run.
Do all small businesses just have to accept that serious maintenance may take the system down for 2-4 hours if that data is not critical to the operation of the business? Or is that unusual for the system to take such a long time to recover?
My backups would have taken less time but this seemed like the easiest first step solution. How much more time would a 7TB database have taken and how can those larger companies deal with that kind of downtime?
September 22, 2010 at 7:55 am
Regular checkDB checks are about the easiest - restore a backup to a secondary server, checkDB that. That way you test out your backup and you do an integrity check at the same time. If that completes successfully you know that your backups are good and your DB is clean.
If you're talking about repair, that's not generally the indicated or recommended solution for corruption. Restore database/filegroup/file/page (as appropriate) often is.
Or if you have mirroring - fail over to the mirror, drop the (former) principal DB, recreate the mirroring. Corruption fixed, (almost) 0 downtime at all.
All depends on how much you're willing to spend on DR and recovery. The more you spend, the quicker you can typically be up after a disaster.
Larger companies typically tolerate very little downtime and have DR plans and redundancies in place to allow that.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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