Date: Thu, 29 Oct 1998 14:45:55 -0800 From: David Greenman <dg@root.com> To: "Matthew N. Dodd" <winter@jurai.net> Cc: Karl Denninger <karl@Denninger.Net>, Hallam Oaks <mlnn4@oaks.com.au>, "hackers@FreeBSD.ORG" <hackers@FreeBSD.ORG> Subject: Re: Multi-terabyte disk farm Message-ID: <199810292245.OAA28199@implode.root.com> In-Reply-To: Your message of "Thu, 29 Oct 1998 12:06:15 EST." <Pine.BSF.4.02.9810291202030.17054-100000@sasami.jurai.net>
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>On Thu, 29 Oct 1998, Karl Denninger wrote: >> > You'd proably only see it in RAID5 mode or if you were -really- beating on >> > your array. Still, with that much memory they should make # of tags >> > supported a tunable. >> >> We beat the SHIT out of our arrays, and the big NFS servers run in RAID 5 >> mode :-) > >But how busy is the controller? 50%? More? > >David G. would probably have more information on the CMD's low performance >modes. (Or rather modes where the limited number of taged commands begins >to impose limits on I/O) It's unlikely that you'd be able to get enough concurrency on any "typical" system to see the tag limit. According to the Adaptec person I talked to, the newer CRD-5440's are further limited to just 32 tags. This would totally kill us on wcarchive. For one thing, you'll rarely ever see any seek optimizations - you have to have several tags queued on a drive before it can optimally reorder them. If you've got 36 drives and only 32 tags, well, you have a big problem. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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