From owner-freebsd-current Tue Mar 21 13:14:53 2000 Delivered-To: freebsd-current@freebsd.org Received: from gndrsh.dnsmgr.net (GndRsh.dnsmgr.net [198.145.92.4]) by hub.freebsd.org (Postfix) with ESMTP id A306E37BD0A; Tue, 21 Mar 2000 13:14:50 -0800 (PST) (envelope-from freebsd@gndrsh.dnsmgr.net) Received: (from freebsd@localhost) by gndrsh.dnsmgr.net (8.9.3/8.9.3) id NAA49370; Tue, 21 Mar 2000 13:14:46 -0800 (PST) (envelope-from freebsd) From: "Rodney W. Grimes" Message-Id: <200003212114.NAA49370@gndrsh.dnsmgr.net> Subject: Re: patches for test / review In-Reply-To: <20000321200438.F966@yedi.iaf.nl> from Wilko Bulte at "Mar 21, 2000 08:04:38 pm" To: wilko@FreeBSD.ORG Date: Tue, 21 Mar 2000 13:14:45 -0800 (PST) Cc: dillon@apollo.backplane.com (Matthew Dillon), phk@critter.freebsd.dk (Poul-Henning Kamp), bright@wintelcom.net (Alfred Perlstein), current@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL54 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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. Your a bit behind the times with that set of numbers for modern SCSI drives. It is now 1 to 16 Mbyte of cache, with 2 and 4Mbyte being the most common. -- Rod Grimes - KD7CAX @ CN85sl - (RWG25) rgrimes@gndrsh.dnsmgr.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message