From owner-freebsd-scsi Tue May 26 16:33:37 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id QAA19575 for freebsd-scsi-outgoing; Tue, 26 May 1998 16:33:37 -0700 (PDT) (envelope-from owner-freebsd-scsi@FreeBSD.ORG) Received: from sendero.simon-shapiro.org (sendero.simon-shapiro.org.142.69.207.in-addr.arpa [207.69.142.25] (may be forged)) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id QAA19556 for ; Tue, 26 May 1998 16:33:29 -0700 (PDT) (envelope-from shimon@sendero.simon-shapiro.org) Received: (qmail 1905 invoked by uid 1000); 27 May 1998 00:34:42 -0000 Message-ID: X-Mailer: XFMail 1.3 [p0] on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <199805262137.PAA00792@panzer.plutotech.com> Date: Tue, 26 May 1998 20:34:42 -0400 (EDT) Reply-To: shimon@simon-shapiro.org Organization: The Simon Shapiro Foundation From: Simon Shapiro To: "Kenneth D. Merry" Subject: Re: DPT install problem Cc: owensc@enc.edu, tom@sdf.com, freebsd-stable@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG, rzig@verio.net Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On 26-May-98 Kenneth D. Merry wrote: > Simon Shapiro wrote... >> On 22-May-98 Raul Zighelboim wrote: >> > As a sidebar; the DOS configuration software can only create arrays >> > with >> > up to 1 mbyte interleave. Is this a limitation on the hardware or the >> > software ? Is (will there be) a way to create an array with a larger >> > interleave (32 megs comes to mind). >> >> An interleave factor larger than 1MB will be very inefficient: >> >> a. The SCSI bus will be used (locked) for long periods. This will >> cause poor multi-tasking response. >> >> b. The cache memory will be able to contain very few stripes. >> >> Also notice that in the context of FreeBSD, anything larger than 64K is >> sort of mute, as the O/S limits all SCSI transfers to that size. I do >> not >> know yet how CAM will do, but suspect it to be the same. > > It will be the same. The 64K limitation is a generic FreeBSD > limitation, so CAM won't change it. CAM won't limit it, though. Here at > Pluto, we've been running large chunks (> 64K) through CAM and the > Adaptec > driver by passing physical memory addresses in through the passthrough > driver. (and therefore you bypass the whole struct buf thing and physio) Ugly :-) We need this type of support in raw devices, though, so userland can pass it in reasonable manner. > If we ever get a buffer chaining (or similar) scheme in place, > it'll be possible to do any size I/O without jumping through hoops. > >> > Thanks, Simon, for a job well done. >> >> Thanx. I am going to get started on CAM port in the next few days. > > Good deal. Contact me via private email about getting access to > the CAM source repository. > > Ken > -- > Kenneth Merry > ken@plutotech.com --- Sincerely Yours, Simon Shapiro Shimon@Simon-Shapiro.ORG 770.265.7340 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message