Date: Thu, 29 Aug 2013 08:59:27 -0700 From: Freddie Cash <fjwcash@gmail.com> To: "Sam Fourman Jr." <sfourman@gmail.com> Cc: FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: NFS on ZFS pure SSD pool Message-ID: <CAOjFWZ6sigqx8LxMHmDvvH7XoNi-GCW=q1YzoXUoDq%2BOOBsC9Q@mail.gmail.com> In-Reply-To: <CAOFF%2BZ0SRDUNuaT73e4jU%2BFZESR35OS8Vo9cU-bV2-zn-HhWDw@mail.gmail.com> References: <CAOFF%2BZ3jNvnWbE5C8LarRE7-SQbB4Q9NJTn01J=FGP9uppKdaw@mail.gmail.com> <1079189088.15197172.1377784177805.JavaMail.root@uoguelph.ca> <CAOFF%2BZ0SRDUNuaT73e4jU%2BFZESR35OS8Vo9cU-bV2-zn-HhWDw@mail.gmail.com>
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On Thu, Aug 29, 2013 at 7:16 AM, Sam Fourman Jr. <sfourman@gmail.com> wrote:
> On Thu, Aug 29, 2013 at 9:49 AM, Rick Macklem <rmacklem@uoguelph.ca>
> wrote:
> > Also, I think there are tunables for the metadata cache in ZFS, which
> > might be useful for increasing the metadata cache sizes, since the probes
> > will be checking metadata (attributes).
>
> Can does anyone here on the list, have clues on where to start with ZFS
> metadata turntables, and a command or two to profile the kernel for CPU
> usage?
>
This will show you how many bytes of the ARC are being used by metadata:
sysctl vfs.zfs.arc_meta_used
You can tune what the max is via:
sysctl vfs.zfs.arc_meta_limit
The default setting is 12.5% (one eighth) of the ARC.
On our servers running dedupe, we set this to around 80% of the ARC, and
set the secondarycache ZFS property to "metadata", in order to keep the DDT
in ARC/L2ARC.
You may want to play with the arc_meta_limit a bit.
--
Freddie Cash
fjwcash@gmail.com
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