Date: Wed, 21 Sep 2011 15:39:58 +0100 From: RW <rwmaillists@googlemail.com> To: freebsd-questions@freebsd.org Subject: Re: UFS journal size Message-ID: <20110921153958.73c1abf1@gumby.homeunix.com> In-Reply-To: <4E79BF44.206@infracaninophile.co.uk> References: <CANmv3=yuQudqqfj8xA3kQkH1XHjSBxgkR5zAB_jwpVWk9RxFeQ@mail.gmail.com> <4E79BF44.206@infracaninophile.co.uk>
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On Wed, 21 Sep 2011 11:41:08 +0100 Matthew Seaman wrote: > On 21/09/2011 10:48, Ross wrote: > > My question is: if I have 4 or 8 GB of RAM should I create 8 or even > > 16 GB journals?.. This seems huge especially if the fs size without > > journal is only 10 gigs. Or the recommended minimum is for systems > > low on RAM? > > The 'twice physical RAM' advice is all about achieving maximum > performance on large filesystems with lots of data writes: IIRC the original justification for 2*ram was as a crude rule-of-thumb to avoid panics. I think the idea was that writing the whole ram into one of the two journalling areas was an extreme case. > You might just as well use plain UFS+Softupdates. Softupdates to > provide the meta-data ordering feature, so that if you do crash and > need to fsck the filesystem, there's not going to be any really nasty > stuff to fix. And in 9.x UFS filesystems (even existing ones) will be able to use journalled soft-updates. This should give a fast fsck without the overheads of full data journalling or background fsck. > Plain UFS because a filesystem of that size will take > about as long to fsck as it would to replay all the journalled but > uncommitted updates. FWIW fsck doesn't replay the journal, it just does a quick check for orphaned files and marks the filesystem as clean - uncommitted updates are left for gjournal.
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