From owner-freebsd-hackers Sat Feb 28 15:25:11 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA03162 for freebsd-hackers-outgoing; Sat, 28 Feb 1998 15:25:11 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from smtp04.primenet.com (smtp04.primenet.com [206.165.6.134]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA03144 for ; Sat, 28 Feb 1998 15:24:45 -0800 (PST) (envelope-from tlambert@usr08.primenet.com) Received: (from daemon@localhost) by smtp04.primenet.com (8.8.8/8.8.8) id QAA16826; Sat, 28 Feb 1998 16:24:42 -0700 (MST) Received: from usr08.primenet.com(206.165.6.208) via SMTP by smtp04.primenet.com, id smtpd016795; Sat Feb 28 16:24:36 1998 Received: (from tlambert@localhost) by usr08.primenet.com (8.8.5/8.8.5) id QAA10147; Sat, 28 Feb 1998 16:24:30 -0700 (MST) From: Terry Lambert Message-Id: <199802282324.QAA10147@usr08.primenet.com> Subject: Re: SCSI Bus redundancy... To: sbabkin@dcn.att.com Date: Sat, 28 Feb 1998 23:24:30 +0000 (GMT) Cc: shimon@simon-shapiro.org, wilko@yedi.iaf.nl, grog@lemis.com, jdn@acp.qiv.com, blkirk@float.eli.net, hackers@FreeBSD.ORG In-Reply-To: from "sbabkin@dcn.att.com" at Feb 28, 98 01:10:44 pm X-Mailer: ELM [version 2.4 PL25] 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 > > > I think Julian's SLICE code has something in that direction. DPT > > > supports INCREASING the size of a RAID-5 array by adding drives. > > > > How can that work? > > Something like > - read N RAID blocks from K disks > - compute new checksum for K+1 disks and write as less number > of RAID blocks but each one of bigger size (K+1/K times) > - add empty blocks at the end of RAID in the added space > > What am I wondering is why nobody did that before ? It's so boring > to rebuild the whole RAID if all you want is to add or remove a disk. You would have to remember to grab the blocks to be relocated with the same O(n) randomness as their allocation. 8-). This is exactly analogous to the FFS extension problem discussed in another thread. Why hasn't it been done? Maybe too many programmers and too few computer scientists? 8-). It's a math problem... ;-). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message