Re: Questions about journals, performance and disk utilization.

[Jeff Mitchell <jeffrey.mitchell@gmail.com>]

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.

Here you go: http://ceph.com/docs/master/rados/operations/placement-groups/

(Notice the lack of any power-of-2 mention  :-)  )

--Jeff