From owner-freebsd-current Fri May 19 20:20:46 2000 Delivered-To: freebsd-current@freebsd.org Received: from freebie.lemis.com (freebie.lemis.com [192.109.197.137]) by hub.freebsd.org (Postfix) with ESMTP id CA33E37B6D0 for ; Fri, 19 May 2000 20:20:34 -0700 (PDT) (envelope-from grog@freebie.lemis.com) Received: (from grog@localhost) by freebie.lemis.com (8.9.3/8.9.0) id MAA61248; Sat, 20 May 2000 12:49:37 +0930 (CST) Date: Sat, 20 May 2000 12:49:37 +0930 From: Greg Lehey To: Matthew Dillon Cc: Matthew Reimer , current@FreeBSD.ORG Subject: Re: Possible Vinum RAID-5 problems? (was: panic: ffs_valloc: dup alloc) Message-ID: <20000520124936.E57670@freebie.lemis.com> References: <39256530.1FD33AA5@vpop.net> <200005191943.MAA40388@apollo.backplane.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0pre2i In-Reply-To: <200005191943.MAA40388@apollo.backplane.com> Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.lemis.com/~grog X-PGP-Fingerprint: 6B 7B C3 8C 61 CD 54 AF 13 24 52 F8 6D A4 95 EF Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Friday, 19 May 2000 at 12:43:28 -0700, Matthew Dillon wrote: > >> Greg Lehey wrote: >>> >>> As far as soft updates goes, basically it's incompatible with Vinum, >>> since there's currently no way of ensuring the sequence of writes >>> across a number of disks. I'm thinking of ways of doing it, but they >>> will cause significant loss in performance. There should be no >>> problems as long as there isn't a crash, of course :-) >> >> Do you mean that softupdates is entirely incompatible with Vinum, or >> just incompatible with Vinum's RAID5? > > Wait a sec... softupdates does not depend on write ordering. > Softupdates issues all non-conflicting writes in parallel and > doesn't care what order they are written to the disk. When > those complete, softupdates will then followup with all the > writes that depend on the original set. Hmm. Maybe I've misunderstood, then. It was my understanding that soft updates writes metadata with WRITE_ORDERED set, and thus avoids having to explicitly wait for completion. It's the WRITE_ORDERED that Vinum doesn't handle correctly. On a single disk, it's just a question of not sorting around a WRITE_ORDERED request. Vinum will keep the WRITE_ORDERED on a single disk, but it won't ensure that a request for the same volume, but which is destined for a different disk, will not be written until after all components of a prior WRITE_ORDERED request for that volume. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message