From owner-freebsd-hackers Wed Mar 4 12:22:24 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id MAA16098 for freebsd-hackers-outgoing; Wed, 4 Mar 1998 12:22:24 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from uni4nn.gn.iaf.nl (osmium.gn.iaf.nl [193.67.144.12]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id MAA15955 for ; Wed, 4 Mar 1998 12:22:00 -0800 (PST) (envelope-from wilko@yedi.iaf.nl) Received: by uni4nn.gn.iaf.nl with UUCP id AA20875 (5.67b/IDA-1.5); Wed, 4 Mar 1998 20:24:02 +0100 Received: (from wilko@localhost) by yedi.iaf.nl (8.8.7/8.6.12) id TAA01281; Wed, 4 Mar 1998 19:29:38 +0100 (MET) From: Wilko Bulte Message-Id: <199803041829.TAA01281@yedi.iaf.nl> Subject: Re: SCSI Bus redundancy... In-Reply-To: from Simon Shapiro at "Mar 3, 98 04:23:24 pm" To: shimon@simon-shapiro.org Date: Wed, 4 Mar 1998 19:29:38 +0100 (MET) Cc: sbabkin@dcn.att.com, tlambert@primenet.com, jdn@acp.qiv.com, blkirk@float.eli.net, hackers@FreeBSD.ORG, grog@lemis.com X-Organisation: Private FreeBSD site - Arnhem, The Netherlands X-Pgp-Info: PGP public key at 'finger wilko@freefall.freebsd.org' X-Mailer: ELM [version 2.4ME+ PL32 (25)] Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG As Simon Shapiro wrote... > > On 03-Mar-98 Wilko Bulte wrote: > > ... > > > Hear hear. RAID parity is also done in hardware these days. Mostly for > > speed reasons. A second reason to go for a standalone RAIDbox is of > > course > > the clustering/multi-host thingy. Backplane RAID is IMHO more for > > low(er)-end solutions. > > Where does that leave kernel RAID? I like controller level RAID because: > > a. Much more flexible in packaging; I can use of-the shelf disks in > off-the-shelf cases if I choose to). Assuming *good* drives, with *good* firmware. This is as you know not as obvious as it sounds ;-) > b. In the case of a DPT, you get better performance and better > reliability, as I have three busses to spread the I/O across, and three > busses to take fatal failures on. Yep. Apart from that customer that had a 3 channel Mylex but used only one to attach drives to. Wanted to save on the hot-plug case for the drives. Well, never mind... You can guess what has happened. 3 channel is the bare minimum IMO. > > This is probably true. You also want to realise that the early production > > units of a given drive model tend to have substantially lower MTBFs. It > > seems when manufacturing plants get the 'feel' for producing a specific > > model MTBF gets better. > > I think the focus has to change: > > * We used to do RAID to protect from hardware failure disrupting service. > In the face of O/S and firmware volatility and buginess, this is absurd; ? I don't quite follow you I think. We *still* do RAID to avoid service disruption. > I think the focus changed from operational feature to insurance policy. Like going bankrupt or collide in midair in case of an aircraft tracking system. > Risk management is something not too many of us is any good at (count the > number of times you/I/we delivered a project on time. > > What does it all mean? I dunno. I leave it to the scientists to ponder. Hm. _ ______________________________________________________________________ | / o / / _ Bulte email: wilko @ yedi.iaf.nl http://www.tcja.nl/~wilko |/|/ / / /( (_) Arnhem, The Netherlands - Do, or do not. There is no 'try' --------------- Support your local daemons: run [Free,Net,Open]BSD Unix -- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message