January 3, 2002 at 8:02 pm
I have always used full backups to backup databases. Tansaction log backups are used for databases that have data constantly being updated. I have never seen the need or logic behind using differential backups. Maybe this is because the largest databases I have ever managed have only been 2.5 GB in size and so can be restored quickly. Are differential backups a must when databases are larger?
Robert Marda
Robert W. Marda
Billing and OSS Specialist - SQL Programmer
MCL Systems
January 3, 2002 at 11:08 pm
Hi
Well not really, it comes more down to recovery time. Applying a series of logs will be slower than applying a single differential. I rarely use them but my DB's range from 1Gb to 10Gb and the transaction counts are nothing too dramatic. If your SLA states XYZ recovery time, then test a full recovery with all the logs, then try the same test but a using a differential backup then apply the last of the remaining logs.
In the end I like things simple, and full + logs is about as simple as you get. If you add differentials in, make sure you document it.
Cheers
Chris
Chris Kempster
www.chriskempster.com
Author of "SQL Server Backup, Recovery & Troubleshooting"
Author of "SQL Server 2k for the Oracle DBA"
January 4, 2002 at 4:35 am
Mine are also small enough and the time window sufficient that I use a daily full plus a demand driven log backup (based on log size). Differential really starts to look good when you can't do a full backup daily.
Andy
January 4, 2002 at 10:38 am
I too have small dbs, so I don't bother, but I worked with a company that had a heavy OLTP load. As a result, they wanted log backups often, so we did every 5 minutes. We timed the differential v full and it was significant different because the changes were concentrated in certain areas. So we decided to do fulls every night and then differentials every 4 hours. Made for a simple restore at almost anytime.
Steve Jones
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