Date: Wed, 4 Mar 1998 19:29:38 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: shimon@simon-shapiro.org Cc: sbabkin@dcn.att.com, tlambert@primenet.com, jdn@acp.qiv.com, blkirk@float.eli.net, hackers@FreeBSD.ORG, grog@lemis.com Subject: Re: SCSI Bus redundancy... Message-ID: <199803041829.TAA01281@yedi.iaf.nl> In-Reply-To: <XFMail.980303162324.shimon@simon-shapiro.org> from Simon Shapiro at "Mar 3, 98 04:23:24 pm"
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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
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