Date: Thu, 21 Jul 2011 18:38:02 +0200 From: Ivan Voras <ivoras@freebsd.org> To: Freddie Cash <fjwcash@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS and large directories - caveat report Message-ID: <CAF-QHFVJpFkMO94SFg403v-mNGRbn8soih67gUrujnzC=tSPFA@mail.gmail.com> In-Reply-To: <CAOjFWZ7x7AM1BvR0KBWM4669rtMgcBBt%2BBP96RppvtSP_gRhJg@mail.gmail.com> References: <j09hk8$svj$1@dough.gmane.org> <CAOjFWZ7x7AM1BvR0KBWM4669rtMgcBBt%2BBP96RppvtSP_gRhJg@mail.gmail.com>
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On 21 July 2011 17:50, Freddie Cash <fjwcash@gmail.com> wrote: > On Thu, Jul 21, 2011 at 8:45 AM, Ivan Voras <ivoras@freebsd.org> wrote: >> >> Is there an equivalent of UFS dirhash memory setting for ZFS? (i.e. the >> size of the metadata cache) > > vfs.zfs.arc_meta_limit > > This sets the amount of ARC that can be used for metadata.=C2=A0 The defa= ult is > 1/8th of ARC, I believe.=C2=A0 This setting lets you use "primarycache=3D= all" > (store metadata and file data in ARC) but then tune how much is used for > each. > > Not sure if that will help in your case or not, but it's a sysctl you can > play with. I don't think that it works, or at least is not as efficient as dirhash: www:~> sysctl -a | grep meta kern.metadelay: 28 vfs.zfs.mfu_ghost_metadata_lsize: 129082368 vfs.zfs.mfu_metadata_lsize: 116224 vfs.zfs.mru_ghost_metadata_lsize: 113958912 vfs.zfs.mru_metadata_lsize: 16384 vfs.zfs.anon_metadata_lsize: 0 vfs.zfs.arc_meta_limit: 322412800 vfs.zfs.arc_meta_used: 506907792 kstat.zfs.misc.arcstats.demand_metadata_hits: 4471705 kstat.zfs.misc.arcstats.demand_metadata_misses: 2110328 kstat.zfs.misc.arcstats.prefetch_metadata_hits: 27 kstat.zfs.misc.arcstats.prefetch_metadata_misses: 51 arc_meta_used is nearly 500 MB which should be enough even in this case. With filenames of 32 characters, all the filenames alone for 130,000 files in a directory take about 4 MB - I doubt the ZFS introduces so much extra metadata it doesn't fit in 500 MB. I am now deleting the session files, and I hope it will not take days to complete...
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