Date: Tue, 21 Jan 2003 12:02:12 +0300 From: Nikita Danilov <Nikita@Namesys.COM> To: Julian Elischer <julian@elischer.org> Cc: Steve Byan <stephen_byan@maxtor.com>, freebsd-fs@FreeBSD.ORG Subject: Re: JFS vs. Soft Updates (again) (was: Re: large filesystem, journaling filesystem support) Message-ID: <15917.3220.652605.965883@laputa.namesys.com> In-Reply-To: <Pine.BSF.4.21.0301201120430.39747-100000@InterJet.elischer.org> References: <37CA8FF0-2CA5-11D7-962B-00306548867E@maxtor.com> <Pine.BSF.4.21.0301201120430.39747-100000@InterJet.elischer.org>
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Julian Elischer writes: > I hate to enter this argument but.... > > > On Mon, 20 Jan 2003, Steve Byan wrote: > [...] > > > > > If you wish to have writes complete to the media in the order in which > > you issued then, then you must either > > a) disable write caching and not use SCSI command queuing for ordered > > writes > > or > > b) enable write caching but do not use SCSI command queuing, and either > > b1) set the FUA bit in the SCSI CDB and not use command queuing for > > ordered writes, or > > b2) follow the ATA write command with a "flush cache" command > > or > > c) enable write caching and SCSI command queuing, but > > c1) set the FUA bit in the SCSI CDB and ensure the command has the > > "ordered task" attribute in its task tag, so that the command will not > > be reordered. > > > > that is good information > maybe the SCSI and ATA guys can experiment on whether any of these modes > gives us acceptable performance. > Linux reiserfs on SCSI devices can run with write-behind caching, and uses write barriers to write transaction commit records. It has been found that performance in this case is identical to just running (unsafely) with write-behind caching, which is much better than using write-through cache. Sorry, I don't have any numbers on this. > > > > [...] Nikita. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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