From owner-freebsd-current Tue Mar 21 11:39:41 2000 Delivered-To: freebsd-current@freebsd.org Received: from uni4nn.gn.iaf.nl (osmium.gn.iaf.nl [193.67.144.12]) by hub.freebsd.org (Postfix) with ESMTP id 4013A37C0E7 for ; Tue, 21 Mar 2000 11:39:34 -0800 (PST) (envelope-from wilko@yedi.iaf.nl) Received: from yedi.iaf.nl (uucp@localhost) by uni4nn.gn.iaf.nl (8.9.2/8.9.2) with UUCP id UAA05057; Tue, 21 Mar 2000 20:25:40 +0100 (MET) Received: (from wilko@localhost) by yedi.iaf.nl (8.9.3/8.9.3) id UAA01311; Tue, 21 Mar 2000 20:04:38 +0100 (CET) (envelope-from wilko) Date: Tue, 21 Mar 2000 20:04:38 +0100 From: Wilko Bulte To: Matthew Dillon Cc: Poul-Henning Kamp , Alfred Perlstein , current@freebsd.org Subject: Re: patches for test / review Message-ID: <20000321200438.F966@yedi.iaf.nl> Reply-To: wilko@freebsd.org References: <20000320111544.A14789@fw.wintelcom.net> <20102.953580112@critter.freebsd.dk> <20000321000435.A8143@yedi.iaf.nl> <200003211729.JAA81170@apollo.backplane.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1i In-Reply-To: <200003211729.JAA81170@apollo.backplane.com>; from dillon@apollo.backplane.com on Tue, Mar 21, 2000 at 09:29:56AM -0800 X-OS: FreeBSD 3.4-STABLE X-PGP: finger wilko@freebsd.org Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Tue, Mar 21, 2000 at 09:29:56AM -0800, Matthew Dillon wrote: > :> > :> I would think that track-caches and intelligent drives would gain > :> much if not more of what clustering was designed to do gain. > : > :Hm. But I'd think that even with modern drives a smaller number of bigger > :I/Os is preferable over lots of very small I/Os. Or have I missed the point? > As long as you do not blow away the drive's cache with your big I/O's, > and as long as you actually use all the returned data, it's definitely > more efficient to issue larger I/O's. Prefetching data that is never used is obviously a waste. 256K might be a bit big, I was thinking of something like 64-128Kb Drive caches tend to be 0.5-1Mbyte (on SCSI disks) for modern drives. I happen to hate write-caching on disk drives so I did not consider that as a factor. > If you generate requests that are too large - say over 1/4 the size of > the drive's cache, the drive will not be able to optimize parallel > requests as well. True. -- Wilko Bulte Arnhem, The Netherlands http://www.tcja.nl The FreeBSD Project: http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message