SQL Server Performance

Log flush waits/s vs Log Flushes/s

Discussion in 'Performance Tuning for DBAs' started by Chappy, Feb 21, 2003.

  1. Chappy New Member

    How do these two performance counters differ?

    In my experience they are always the same, im wondering if there are circumstances when log flushes could be deferred and result in log flush waits being greater than log flushes for a given log entry.
  2. bradmcgehee New Member

    See this url for information on the SQLServer<img src='/community/emoticons/emotion-2.gif' alt=':D' />atabases:Log Flushes/sec counter counter (at the bottom of the page):<br /><br /<a target="_blank" href=http://www.sql-server-performance.com/performance_monitor_counters_sql_server.asp>http://www.sql-server-performance.com/performance_monitor_counters_sql_server.asp</a><br /><br />In essense, this is the number of actual commits (log flushes) that are occuring per second.<br /><br />I don't have any info on log flush waits/second on my website, but it refers to the number of commits (or future log flushes) that need to be done, but can't because they are waiting their turn.<br /><br />I checked one of my busiest servers, and like you, the two numbers were equal, which appears to contradict what I just said. I would have guessed that my log flush waits/sec would have been zero.<br /><br />I don't know why this is, except perhaps a bug with the counter, or mistake in the explanation of the counter.<br /><br />I would also guess that under very heavy I/O loads, assuming the log flush wait/sec really works, that it would get bigger than the log flushes/sec.<br /><br />------------------<br />Brad M. McGehee<br />Webmaster<br />SQL-Server-Performance.Com

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