Hello guys,

Thank you so much for your responses really appreciate it. But I would like
to mention one more thing which I forgot in my last email is that I am
going to use this storage for openstack VM's. So still the answer will be
the same that I should use 1GB for wal?

On Wed, 14 Aug 2019 at 05:54, Mark Nelson <mnel...@redhat.com> wrote:

> On 8/13/19 3:51 PM, Paul Emmerich wrote:
> > On Tue, Aug 13, 2019 at 10:04 PM Wido den Hollander <w...@42on.com>
> wrote:
> >> I just checked an RGW-only setup. 6TB drive, 58% full, 11.2GB of DB in
> >> use. No slow db in use.
> > random rgw-only setup here: 12TB drive, 77% full, 48GB metadata and
> > 10GB omap for index and whatever.
> >
> > That's 0.5% + 0.1%. And that's a setup that's using mostly erasure
> > coding and small-ish objects.
> >
> >
> >> I've talked with many people from the community and I don't see an
> >> agreement for the 4% rule.
> > agreed, 4% isn't a reasonable default.
> > I've seen setups with even 10% metadata usage, but these are weird
> > edge cases with very small objects on NVMe-only setups (obviously
> > without a separate DB device).
> >
> > Paul
> I agree, and I did quite a bit of the early space usage analysis.  I
> have a feeling that someone was trying to be well-meaning and make a
> simple ratio for users to target that was big enough to handle the
> majority of use cases.  The problem is that reality isn't that simple
> and one-size-fits all doesn't really work here.
> For RBD you can usually get away with far less than 4%.  A small
> fraction of that is often sufficient.  For tiny (say 4K) RGW objects
> (especially objects with very long names!) you potentially can end up
> using significantly more than 4%. Unfortunately there's no really good
> way for us to normalize this so long as RGW is using OMAP to store
> bucket indexes.  I think the best we can do long run is make it much
> clearer how space is being used on the block/db/wal devices and easier
> for users to shrink/grow the amount of "fast" disk they have on an OSD.
> Alternately we could put bucket indexes into rados objects instead of
> OMAP, but that would be a pretty big project (with it's own challenges
> but potentially also with rewards).
> Mark
> _______________________________________________
> ceph-users mailing list
> ceph-users@lists.ceph.com
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

Thanks and Regards,

Hemant Sonawane
ceph-users mailing list

Reply via email to