Date: Wed, 21 Sep 2011 08:40:18 -0500 From: Doug Poland <doug@polands.org> To: Ross <basarevych@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: UFS journal size Message-ID: <20110921134018.GA48785@polands.org> In-Reply-To: <CANmv3=yuQudqqfj8xA3kQkH1XHjSBxgkR5zAB_jwpVWk9RxFeQ@mail.gmail.com> References: <CANmv3=yuQudqqfj8xA3kQkH1XHjSBxgkR5zAB_jwpVWk9RxFeQ@mail.gmail.com>
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On Wed, Sep 21, 2011 at 12:48:25PM +0300, Ross wrote: > Quoting the manpage: > > -s jsize Specifies size of the journal if only one provider is > used for both data and journal. The default is one > gigabyte. Size should be chosen based on provider's > load, and not on its size; recommended minimum is twice > the size of the physical memory installed. It is not > recommended to use gjournal for small file systems > (e.g.: only few gigabytes big). > > 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? > My experience has shown that speed of the underlying filessystem has a huge impact on the required size of the journal. I have a system running hardware RAID-10 on a 3Ware SATA controller. On a 100G partition, rsync would regularly cause a panic until I got my journal up above 10G. This particular host has only 1G of RAM and a single 3.4GHz P4 CPU. Sizing this particular box using gjournal was painful until I got the journal sizes large enough. It turns out the journals had to be so large (for the infrequent write burst) that a significant amount of disk was chewed up for journals that were mostly unused. If I had to do it over again, I would have not used gjournal and simply used softupdates. YMMV -- Regards, Doug
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