Date: Sun, 25 Nov 2007 17:10:13 +0100 From: Espen Tagestad <espen@modula.no> To: Tom Judge <tom@tomjudge.com> Cc: freebsd-stable@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: SAS5IR performance issue with Dell 860 Message-ID: <47499E65.4050206@modula.no> In-Reply-To: <47499710.1050402@tomjudge.com> References: <47496BE1.8080206@modula.no> <47499710.1050402@tomjudge.com>
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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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