On Tue, May 12, 2015 at 10:38 PM, Chad William Seys
<cwseys@xxxxxxxxxxxxxxxx> wrote:
> Hi Ilya and all,
> Thanks for explaining.
> I'm confused about what "building" a crushmap means.
> After running
> #ceph osd crush tunables hammer
> data migrated around the cluster, so something changed.
> I was expecting that 'straw' would be replaced by 'straw2'.
> (Unfortunately I did not dump the crushmap prior to setting tunables to
> hammer, so I don't know what change did occur.)
> So I guess setting tunables to hammer is not "building" a crushmap.
> Could you give examples? Would creating a new pool on the cluster now use
> straw2?
No, pools use crush rulesets. "straw" and "straw2" are bucket types
(or algorithms).
As an example, if you do "ceph osd crush add-bucket foo rack" on
a cluster with firefly tunables, you will get a new straw bucket. The
same after doing "ceph osd crush tunables hammer" will get you a new
straw2 bucket, with the rest of your buckets remaining unaffected.
straw buckets are not going to be replaced with straw2 buckets, that's
something you as an administrator can make a choice to do.
Thanks,
Ilya
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