Tom Judge wrote:
Espen Tagestad wrote:
We recently bought 3 new Dell 860 servers with the onboard SAS5/IR
SATA RAID-controller. They seem to be quite well spec'ed servers with
management and everything - but I am experiencing av major performance
issue with the disc i/o. On write I get at max 7-8MB/sec, while read
gives a bit more (11MB/sec). I tried first with 6.2-RELEASE, and then
upgraded to 6.3-PRERELEASE without any better results.
You will also need to set the hw.mpt.enable_sata_wc sysctl in loader.conf.
There isn't any hw.mpt.enable_sata_wc sysctl available on my systems. It
is 6.3-PRERELEASE, but as I recon there wasn't any *mpt* sysctls on the
latest 6.2-RELEASE either. Is it deprecated? Is there any other options?
I can see a hw.ata.wc but that one is set to 1 which I presume equals
enabled.
Anyway - the write cache, is that something that is set on the raid
controller, or is it a buffer in the FreeBSD kernel that takes care of
the caching? As the commit note you sent me said - to ensure absolutely
best data integrity the write cache should be left switched off. But
write performance of 7-8MB/sec is just too low for that - is the
controller /sata drives really that slow?
--
med vennlig hilsen / with regards,
Espen Tagestad
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