SQLServer Differential Backups make a lot of sense...they backup only what has changed. However, it seems that many Database Administrators choose not to leverage them. When digging into reasons for this, it is often because DBAs prefer to avoid some risk associated with Differential Backups.
First, a Differential Backup requires the last Full backup with which it is associated. If that Full Backup has been corrupted, deleted, or moved, that Differential Backup is rendered useless.
Additionally, if a higher percentage of data has changed since the last backup, it may not make sense to do a Differential Backup. A Full Backup should be taken. SQLServer Differential backups will run regardless of the amount of data that has changed.
Quest's SQLServer Backup and Recovery solution, Litespeed, provides a way to mitigate that risk. It's called 'Fast Compression'. Though the feature name is not inaccurate (it is fast and it does compress), I've always thought a more suitable name for it might be 'Smart Differential' to highlight its primary advantage.
With Litespeed's Fast Compression feature, before running the Differential Backup, this patented technology will do two things:
1. Litespeed checks to confirm that the associated Full Backup exists, it is where it should be, and it is valid. If Litespeed cannot verify the last backup, it runs a Full Backup instead.
2. Litespeed checks to determine how much data has changed. The default threshold is 35% (but this is customizable). If it is above that threshold, Litespeed runs a Full Backup instead.
* (Click on images to enlarge)
There are storage and time savings to be had as a result of using the Fast Compression feature as well.
Here is an example of some test results:
- 5 TB data
- 85% compression
- 3.5% daily data change
- 14 days of backups
- 250 MB/Sec backup rate
Experience the difference Litespeed can make with your SQLServer backups.
For more information and to download a trial copy to evaluate, click here -> Quest Litespeed
