NFS on ZFS pure SSD pool

[Freddie Cash]

On Thu, Aug 29, 2013 at 7:16 AM, Sam Fourman Jr. <sfourman at gmail.com> wrote:

> On Thu, Aug 29, 2013 at 9:49 AM, Rick Macklem <rmacklem at 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 at gmail.com