Date: Fri, 27 Feb 1998 19:36:02 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: Greg Lehey <grog@lemis.com> Cc: hackers@FreeBSD.ORG, blkirk@float.eli.net, jdn@acp.qiv.com, Wilko Bulte <wilko@yedi.iaf.nl> Subject: Re: SCSI Bus redundancy... Message-ID: <XFMail.980227193602.shimon@simon-shapiro.org> In-Reply-To: <19980228134228.40320@freebie.lemis.com>
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On 28-Feb-98 Greg Lehey wrote: ... >> DPT arrays? Simple; you make an ioctl call into the DPT driver, I >> write a message to the controler, specifying which disk to add to >> which array, the controller starts a hot rebuild, etc. The details >> escape me right now, but I belive it is doable. Why would you want >> to do that? No idea... :-) > > I was thinking more about what the ioctl call does. Raid 5 spreads > data in stripes over all drives (or subdisks if you're using a > Veritas-like volume manager). Add a drive, and you break this > mapping. The only way to rearrange is to rewrite all the disks. Is > that what they do? Or are they cheating in some manner? ( At some point in this thread MarkS (from DPT) is going to enter the thread and either explain it properly or tell me to stop violating the NDA I so cleverly signed :-) the IOCTL does nothing more than package a SCSI command, ship it to the controller, wait for the reply and ship that back. The rest is done in the controller. I do not think it re-writes the whole disk array. there is no real need for that. I think there is some hardware support for some of this stuff, and that DPT people know few things I do not. Once I clear my desk of what I am messing up now, I'll look into it a bit better. Simon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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