From owner-freebsd-hackers Thu Oct 29 14:45:53 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id OAA05054 for freebsd-hackers-outgoing; Thu, 29 Oct 1998 14:45:53 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from implode.root.com (implode.root.com [198.145.90.17]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id OAA05029 for ; Thu, 29 Oct 1998 14:45:43 -0800 (PST) (envelope-from xroot@implode.root.com) Received: from implode.root.com (localhost [127.0.0.1]) by implode.root.com (8.8.5/8.8.5) with ESMTP id OAA28199; Thu, 29 Oct 1998 14:45:55 -0800 (PST) Message-Id: <199810292245.OAA28199@implode.root.com> To: "Matthew N. Dodd" cc: Karl Denninger , Hallam Oaks , "hackers@FreeBSD.ORG" Subject: Re: Multi-terabyte disk farm In-reply-to: Your message of "Thu, 29 Oct 1998 12:06:15 EST." From: David Greenman Reply-To: dg@root.com Date: Thu, 29 Oct 1998 14:45:55 -0800 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >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