Date: Sun, 25 Nov 2007 16:18:50 +0000 From: Tom Judge <tom@tomjudge.com> To: Espen Tagestad <espen@modula.no> Cc: freebsd-stable@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: SAS5IR performance issue with Dell 860 Message-ID: <4749A06A.1000409@tomjudge.com> In-Reply-To: <47499E65.4050206@modula.no> References: <47496BE1.8080206@modula.no> <47499710.1050402@tomjudge.com> <47499E65.4050206@modula.no>
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Espen Tagestad wrote: > 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? > > Please read http://unix.derkeiler.com/Mailing-Lists/FreeBSD/stable/2007-07/msg00347.html You will have to set the sysctl in /boot/loader.conf and reboot the system for the changes to take affect. Tom
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