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size of DB for diff backups

Posted on 2011-02-22
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Last Modified: 2012-05-11
at what size of the database is differential backups more recommended?

(like >100 GB etc)- because if the database is smaller, the full backup will be fast enough.
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Question by:anushahanna
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Raja Jegan R earned 125 total points
ID: 34950050
I personally won't prefer Differential backups and would go for Full Backup with Transactional Log backup.

Say if you have Diff backup scheduled to run every 2 hrs, then

First Diff Backup = X size
Second Diff Backup = First Backup + Y Size
and so on..

Thereby occupying more of your disk space and your disk utilization is not good.
Instead having a full backup with purging older full backups or full backups with transactional log backup would be a good idea..
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by:slam69
slam69 earned 125 total points
ID: 34950231
Agree with teh above and if you have a Dr backup and are doing backups look to log ship your tran logs to cut your restoration time down.... whilst i know a lot of people do like them ive never been able to get value out of diff backups when looking at the space implications required for storing them
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by:rajeevnandanmishra
rajeevnandanmishra earned 125 total points
ID: 34950436
Hi,

While agreeing to the above comments, I would still strongly believe that taking the differential backup is not about only the size of database. The differential backup, run over the transaction log and  take only the backup of the activities performed after the last Full Backup. And that is comparatively very very small, considering any database size.  Also the time in which you should schedule your differential backup, is actually the duration for which a maximum loss is acceptable. Like if you have scheduled the diff backup for 1 hour, then you are accepting that a maximum loss of 1 hour is acceptable to the user.

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by:rocky_lotus_newbie
rocky_lotus_newbie earned 125 total points
ID: 34952315
It varies froom Database to Database depending on the data access patterns. FOr some databases, if most of the pages are updated between successive differential backups, then the differential back up is as big as the full backup. In this case, it is not ideal. On the other hand if the number of pages modified is small, differential backups are best bet.

The Main advantage of Differential Backups is for Data Recovery.

I normally configure differential backups for every 4 to 6 hours. Just to make sure the recoveries are faster in case of a disaster.

However, if there is space constraint, we need to go with just the Transaction Log Backups.
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by:anushahanna
ID: 34953130
thanks for your helpful feedback.
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