From owner-freebsd-hackers Fri Feb 27 18:36:19 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id SAA25206 for freebsd-hackers-outgoing; Fri, 27 Feb 1998 18:36:19 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from smtp01.primenet.com (smtp01.primenet.com [206.165.6.131]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id SAA25164 for ; Fri, 27 Feb 1998 18:35:53 -0800 (PST) (envelope-from tlambert@usr06.primenet.com) Received: (from daemon@localhost) by smtp01.primenet.com (8.8.8/8.8.8) id TAA04169; Fri, 27 Feb 1998 19:35:48 -0700 (MST) Received: from usr06.primenet.com(206.165.6.206) via SMTP by smtp01.primenet.com, id smtpd004127; Fri Feb 27 19:35:42 1998 Received: (from tlambert@localhost) by usr06.primenet.com (8.8.5/8.8.5) id TAA22897; Fri, 27 Feb 1998 19:35:37 -0700 (MST) From: Terry Lambert Message-Id: <199802280235.TAA22897@usr06.primenet.com> Subject: Re: SCSI Bus redundancy... To: grog@lemis.com (Greg Lehey) Date: Sat, 28 Feb 1998 02:35:36 +0000 (GMT) Cc: shimon@simon-shapiro.org, wilko@yedi.iaf.nl, jdn@acp.qiv.com, blkirk@float.eli.net, hackers@FreeBSD.ORG In-Reply-To: <19980228110827.36052@freebie.lemis.com> from "Greg Lehey" at Feb 28, 98 11:08:27 am 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? Take a set of devices: [ ] [ ] [ ] The kernel views these as linear arrays of blocks. Steal the first block and/or cylinder and put: struct ccd_label { char signature[ 20]; /* "This is a CCD device"*/ time_t timestamp; /* set created this time*/ long ident; /* set's additional uniquifier*/ long item; /* piece number ...*/ long of; /* of...*/ }; on the front of it. Then you have a CCD SLICE manager that claims these things, and when all N item's of an N item device "arrive", it exports another device that's the agregate of N devices. It works because the SLICE code implements "arrival" events. Personally, I want to use "arrival" events to trigger mounts. 8-). The mapping into the FS hierarchy is a seperate problem altogether. Combine this with "soft readonly" to go with you "soft updates", and you should be able to just turn things off and turn them on and not need fsck's or have mount problems, etc.. 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