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Accepted
Edoode
Asked: 2009-07-08 11:31:09 +0800 CST

How can I improve SQL server mirroring performance

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(reposted from stackoverflow)

I've setup SQL server mirroring, using 2 SQL server 2005 standard editions. When the application is being stressed, response times increase 10-fold. I've pinpointed this to the mirror, because pausing the mirror shows acceptable response times.

What options are available for achieving better performance? Note that I'm using Standard Edition, so the excellent High Performance Mode is unavailable.

The server are in the same rack, connected to a gigabit switch.

Here's the code used to create the endpoints:

CREATE ENDPOINT [Mirroring] 
    AUTHORIZATION [sa]
    STATE=STARTED
    AS TCP (LISTENER_PORT = 5022, LISTENER_IP = ALL)
    FOR DATA_MIRRORING (ROLE = PARTNER, AUTHENTICATION = WINDOWS NEGOTIATE
, ENCRYPTION = REQUIRED ALGORITHM RC4)
sql-server sql-server-2005 database-mirroring mirroring endpoint

2 Answers

  1. While pausing the mirror helps it may not be the actual cause of your trouble. In my experience, using a synchronous mirror only doubles the response time. If you're seeing a response time that gets worse with higher loads, something else is likely to be afoot.

    A few things to think about and try:

    • Check that the server is not underpowered (CPU/memory)
    • Check that the network isn't the bottleneck (by directly connecting the 2 SQL servers and forcing the mirroring traffic to go over that direct link)
    • Check that I/Os aren't the bottleneck (although this seems unlikely to me given the 10x response time increase only with mirroring on). The usual stuff applies: better hardware RAID/cache, separate devices, ...
    • High performance mode is asynchronous. If that's okay with you, then you could use replication rather than mirroring. (I forget the MS term for this feature.)
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  2. Best Answer

    Does the link between the principle and mirror have sufficient bandwidth to cope with the transaction log generation at the principle?

    Are your log files optimised? See these links:

    http://www.sqlskills.com/BLOGS/KIMBERLY/post/8-Steps-to-better-Transaction-Log-throughput.aspx

    http://sqlblog.com/blogs/linchi_shea/archive/2009/02/09/performance-impact-a-large-number-of-virtual-log-files-part-i.aspx

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