Date: Tue, 17 Feb 2009 15:25:27 -0600 From: Tom Judge <tom@tomjudge.com> To: Sebastiaan van Erk <sebster@sebster.com> Cc: freebsd-performance@freebsd.org Subject: Re: Extremely slow write speeds to disk : FreeBSD 7.1 and Dell SAS 6/iR Adapter Message-ID: <499B2B47.2000300@tomjudge.com> In-Reply-To: <499672F1.4060109@sebster.com> References: <200902210616.GAA14352@sopwith.solgatos.com> <499672F1.4060109@sebster.com>
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Sebastiaan van Erk wrote: > Dieter wrote: >>>> But the issue is that writing to disk is extremely slow...i.e. 14Mb >>>> per >>>> second.... >>>> >>>> If I install any other linux distribution, like CentOS, write speek is >>>> the way it should be..it averages around 190Mb+ per second >>>> >>>> I was hoping if it were at all possible for you to assist me in with a >>>> later RAID Controller Driver for the SAS 6/iR Adapter >>>> >>> Try: >>> hw.mpt.enable_sata_wc=1 >>> in /boot/loader.conf and reboot. >>> >>> Assuming you are using SATA drives, the write cache is disabled by >>> default. This reenables it. The mpt manpage holds more information. >>> >> >> Just keep in mind that turning the disk's write cache on puts your >> data at risk. :-( >> >> The correct solution is NCQ. > Just wondering, if you have a battery on your RAID array, is this a > problem? Wouldn't the cache get written anyway in case of a crash? > > Regards, > Sebastiaan Hi, hw.mpt.enable_sata_wc tunable enables the on disk write cache not the controller write cache. Tom
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