[zfs-discuss] One dataset per user?

Arne Jansen
2010-06-22T20:08:38Z

Paul B. Henson wrote:
> On Sun, 20 Jun 2010, Arne Jansen wrote:
>
>> In my experience the boot time mainly depends on the number of
datasets,
>> not the number of snapshots. 200 datasets is fairly easy (we have
>7000,
>> but did some boot-time tuning).
>
> What kind of boot tuning are you referring to? We''ve got about 8k
> filesystems on an x4500, it takes about 2 hours for a full boot cycle which
> is kind of annoying. The majority of that time is taken up with NFS
> sharing, which currently scales very poorly :(.

As you said most of the time is spent for nfs sharing, but mounting also
isn''t
as fast as it could be. We found that the zfs utility is very inefficient as
it does a lot of unnecessary and costly checks. We set mountpoint to legacy
and handle mounting/sharing ourselves in a massively parallel fashion (50
processes). Using the system utilities makes things a lot better, but you
can speed up sharing a lot more by setting the SHARE_NOINUSE_CHECK environment
variable before invoking share(1M). With this you should be able to share your
tree in about 10 seconds.

Good luck,
Arne

>
> Thanks...
>
>