
SQL Server & turning RAID Cache Off
Colin,
I have seen cases where the RAID controller cache has caused some
performance degredation. This has to do with the interaction between the
checkpoint process and the controller cache. The rate at which the
checkpoint process runs is regulated by the speed of writes to your disk
drives. With a RAID controller cache these writes are very short, on the
order of 1-2 ms. This causes the checkpoint process to immediately return
and write out more checkpoint data until the number of writes fills up the
controller cache, thus shutting it off. This can degrade performance. The
checkpoint process is regulated by the parameter MAX ASYNC IO.
I hope that this helps.
Ed
--
Edward Whalen
President
Performance Tuning Corporation
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