Date: Thu, 27 May 2004 04:51:09 +0200 From: Matthias Andree <ma@dt.e-technik.uni-dortmund.de> To: Brad Knowles <brad.knowles@skynet.be> Cc: current@freebsd.org Subject: softupdates and caches/tagged queuein (was: Softupdates a mount option?) Message-ID: <m3r7t6mvky.fsf_-_@merlin.emma.line.org> In-Reply-To: <p06002069bcdaadf2ebd0@[10.0.1.3]> (Brad Knowles's message of "Wed, 26 May 2004 22:28:41 %2B0200") References: <40B4ECC8.50808@fer.hr> <p06002069bcdaadf2ebd0@[10.0.1.3]>
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Brad Knowles <brad.knowles@skynet.be> writes: > At 9:15 PM +0200 2004/05/26, Ivan Voras wrote: > >> This has been really nagging me for a long time: Why aren't softupdates >> made a mount option (like 'sync' and 'async')? Do I remember correctly >> that it is done so in NetBSD (where it's called softdeps), so it's doable? > > You need to read the documentation from Kirk. In short, this > was intentional -- the goal is that this feature will be turned on > permanently, at which point there's no sense in having yet another > useless mount option laying around. IIRC, the license is written such > that you are not *allowed* to make this a mount option, for this reason. > > Kirk is really serious about this. You should read the Ganger & > Platt paper, as well as the other documentation written by Kirk on this > subject. Speaking of which, does this fine file system (softupdates) know how to use - ordered tags (SCSI) - flush cache commands (ATA) (or other barrier approaches) to enforce write order where necessary? I'm wondering a bit for one of my SCSI drive defaults to (control page) queue algorithm modifier = 1 and (caching page) WCE = 1 which means it can reorder at will unless someone uses ordered tags or the do-this-now tag (I forgot the name) - and this discussion is a bit "hot" in the Linux lists ATM. -- Matthias Andree Encrypted mail welcome: my GnuPG key ID is 0x052E7D95
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