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i will need to do differential backups every 15min - 1 hours. we are still deciding what this requirement should be. the entire DB is about 3gb and we do about 1 mb of changes to it per minute. does this mean that the differential backup would be anywhere from 15mb to 60mb?

am i really going to slow down my server? it's a 64 bit windows 2008, about 14 gigs of ram

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up vote 1 down vote accepted

As discussed in the other question (, you really need to be using transaction log backups for this. Whoever is refusing to allow Full recovery mode but wants 15 minute recovery should be fired.

Because these are differential, not incremental, backups, the differential backup is between the last full backup and the present time. Thus, if you take a Full backup, then do differentials with 1MB of changes per minute, then in 30 minutes you'll use (1+2+3+4+5+6...)MB of backup. This is unsustainable. This use case is what transaction log backups are designed for.

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thank you again for baring with me. but this guy is saying that he does NIGHTLY DIFFERENTIAL and only full weekly. so how is it possible that he does several differentials without doing a full back up??… – l--''''''---------'''''''''''' Oct 27 '10 at 18:15
Each differential is the diff to the full backup. For example, let's say I do a Full backup on Saturday night, then diffs the rest of the week. To restore to Sunday's backup, I'd restore the Saturday full, then the Sunday diff. To restore to Tuesday's backup, I'd restore the Saturday full, then Tuesday's diff. – phoebus Oct 27 '10 at 18:17
got it!!! thank so much. i am going to fire this guy – l--''''''---------'''''''''''' Oct 27 '10 at 18:18
For a database of only 3GB I'd do a full backup nightly. Your scenario for a quick Recovery Point Objective is the whole purpose of transaction logs and their backups though. – hmallett Oct 27 '10 at 18:37

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