DB Mirroring Tips


Here are some essential things to consider when trying to tune a DB mirroring setup. They revolve round the following concepts:

  • The effect of Virtual Log Files (VLFs) on recovery and therefore failover times
  • The interplay (or lack thereof) between mirroring and some other SQL Server engine features
  • Network speed and issues


  1. Be on the latest available Service Pack and Cumulative Update for SQL 2005 or 2008. There are many issues related to mirroring which are fixed in these updates. Some of the key ones which I have seen are given below.
  • The remedial steps for this set of problems revolves round fixing the Virtual Log File Fragmentation issues, such as what is described by Kimberly Tripp. The relevant blog posts are:
  • You should also be aware of the article in http://support.microsoft.com/kb/937531 (The shrink operation is not duplicated on the mirror database when you use database mirroring in SQL Server 2005)
  • If you are using MSDTC transactions with a database which is mirrored, please consider fact that it is not officially supported, as the below articles.
  • For the networking side, the key things to consider are given below.

I will keep adding to this post as I receive additional information. In the meantime, I hope you stay informed and therefore hopefully avoid known issues with mirroring.

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