[lustre-discuss] zfs -- mds/mdt -- ssd model / type recommendation

[Peter Kjellström]

On Tue, 5 May 2015 15:11:18 +0000
Patrick Farrell <paf at cray.com> wrote:

> My understanding is it's primarily ZFS rather than ZFS+Lustre, but
> the issue is that the Lustre MDT does a lot of IO in a manner that
> ZFS is not (currently) great at handling.   As I understood, the
> fixes will be in ZFS, not the Lustre layers above it.

One thing that will be in the lustre layer is lustre supporting ZIL. As
it stands today you can't move the intentlog to a fast NVRAM simply
because lustre (unlike zfs posix layer) doesn't use intent log.

As I understood it people originally hoped that this would make it into
2.7.0 but that was waay optimistic. Also many systems in production use
osd_*_sync_delay_us to skip the very expensive pool sync.

/Peter K