Date: Fri, 27 May 2005 12:15:12 -0600 From: Scott Long <scottl@samsco.org> To: Garrett Wollman <wollman@csail.mit.edu> Cc: FreeBSD Current <freebsd-current@FreeBSD.ORG> Subject: Re: Disable read/write caching to disk? Message-ID: <429763B0.2060705@samsco.org> In-Reply-To: <17047.25282.72131.519040@khavrinen.csail.mit.edu> References: <4295D51F.50106@centtech.com> <429606D9.6080602@cs.tu-berlin.de> <42960ACB.7090801@cs.tu-berlin.de> <42960CFE.4060307@centtech.com> <42960F8F.2050109@samsco.org> <42961195.30608@centtech.com> <429613FB.80100@samsco.org> <42968AD4.3020603@centtech.com> <A70C5E4F-D9F9-4756-8AC2-591462E338DE@shire.net> <4296997C.9030700@samsco.org> <20050526235852.M54386@lexi.siliconlandmark.com> <42969C1B.5010301@samsco.org> <17047.25282.72131.519040@khavrinen.csail.mit.edu>
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Garrett Wollman wrote: > <<On Thu, 26 May 2005 22:03:39 -0600, Scott Long <scottl@samsco.org> said: > > >>is just as much work as porting GFS, if not more, since UFS/FFS is >>closely tied to the buffer cache and block layers on BSD, and divorcing >>probably would be quite difficult. > > > For multiple writers, probably so. For the single-writer case, I > don't think so, since the readers can mount a snapshot while the > writer mounts the read-write view. Well, having a writer is pointless if the readers are stuck on a snapshot. Also, I'm not exactly sure how dirty buffers get flushed to disk in the case of a snapshot. Recall that the snapshot file only save the deltas of the old data, and flushing those deltas to disk is still under the control of the VM/buffer/cache system. You'd probably still have to have some sort of inter-computer synchronization system in place. > > All this would be a lot easier if we had a storage manager more like > ZFS's. > Well, ZFS doesn't really exist yet, so it's hard to draw a comparison ;-) Scott
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