This question has already been asked but without a clear answer (for me anyway).
Previous threads:
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How to enable write caching on domain controller
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Override: The driver disabled the write cache on device
I understand the reason behind why Write Cache is disabled on a system disk of a server machine promoted to a DC -- this precaution will avoid the loss of AD database if there is a power loss.
But what if a UPS backup is used? Will this also be a problem?
I use UPS power backup with SBS 2008. When I run the Exchange Performance Troubleshooter, there is a significant performance difference between write cache enabled and disabled. Just for comparison, using the CrystalDiskMark (ver 3.0.2 x64) tool, a sequential
write of 1000MB block increases from 79MB/s (write cache disabled) to nearly double 148MB/s (write cache enabled). I came to a conclusion that if write-cache is enabled, I don't need to replace the system disk to meet the performance requirements indicated
by Exchange Performance Troubleshooter.
However, there is no definitive answer as to whether enabling write cache should be avoided altogether other than indicating "... it is not a good idea to override" kind of answer.
The following registry hack works fine to to prevent the OS from disabling the write cache (but as expected, generates a warning on start-up with event ID 13512 indicating that File Replication Service has detected enabled write cache).
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[HKLM\System\CurrentControlSet\Services\NTDS\Parameters]
"DSA Heuristics"="1"
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the above value being type REG_SZ
My specific question is therefore,
for an SBS 2008 server protected by a UPS power backup, is it ok to prevent the OS from disabling the write cache (and take advantage of the improved HDD access performance)? If it is not a good idea, could you please be more objective by giving operational
issues/reasons? Many thanks.