Mark Nelson wrote:
On 01/22/2013 03:50 PM, Stefan Priebe wrote:
Hi,
Am 22.01.2013 22:26, schrieb Jeff Mitchell:
Mark Nelson wrote:
It may (or may not) help to use a power-of-2 number of PGs. It's
generally a good idea to do this anyway, so if you haven't set up your
production cluster yet, you may want to play around with this.
Basically
just take whatever number you were planning on using and round it
up (or
down slightly). IE if you were going to use 7,000 PGs, round up to
8192.
As I was asking about earlier on IRC, I'm in a situation where the docs
did not mention this in the section about calculating PGs so I have a
non-power-of-2 -- and since there are some production things running on
that pool I can't currently change it.
Oh same thing here - did i miss the doc or can someone point me the
location.
Is there a chance to change the number of PGs for a pool?
Greets,
Stefan
Honestly I don't know if it will actually have a significant effect.
ceph_stable_mod will map things optimally when pg_num is a power of 2,
but that's only part of how things work. It may not matter very much
with high PG counts.
Yeah, that's why I said *if* it matters, once someone runs suitable benchmarks, please provide a resilvering mechanism :-)
I'd be interested in figuring out the right way to migrate an RBD from one pool to another regardless.
--Jeff
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