Transaction Log Backup Affecting Applications Performance

Question

We have a database around terabytes of data. We are taking FULL backup every week, differential backup daily and transaction log backup after every hour. Sometimes this transaction log backup takes some time to complete (around 10-15 minutes). In this period we find that application(s) performance affects a lot(normally very slow) that use the same database.

Does transaction log backup affect the performance of the application? If yes, then how to make speedup the process of taking transaction log backup?

Answer 1

Does transaction log backup affect the performance of the application?

The transaction log backup reads from the transaction log file and writes to the backup location. The application writes to the transaction log file when it changes the database. If the log file or the log backup location and the database files or tempdb files are on the same disk (or even perhaps on the same SAN controller), then the log backup could impact access to those files too.

Capturing a snapshot of the wait stats during the application slowness should provide more details on what impact the backup is having.

Taking the backups more frequently will spread out the impact. But you also may need more storage resources (more or faster disks) for this database. With large databases you need to provide enough resources for both operating and maintaining the database, and maintenance tasks (like log backups, index maintenance, schema modification) can require significant additional resources.

Answer 2

A database that big will most likely have a lot of activity going on and your transaction log backup will be pretty big. 10-15 is a really long time for this to run, I’m surprised you aren’t having it fill up before the backup.

Try running them every 10 minutes, will take much less time and impact will be less