From: Mark Nelson <mark.nelson@inktank.com>
To: Stefan Priebe <s.priebe@profihost.ag>
Cc: Jeff Mitchell <jeffrey.mitchell@gmail.com>,
martin <martin@skytech.dk>,
"ceph-devel@vger.kernel.org" <ceph-devel@vger.kernel.org>
Subject: Re: Questions about journals, performance and disk utilization.
Date: Tue, 22 Jan 2013 15:57:02 -0600 [thread overview]
Message-ID: <50FF0B2E.6010301@inktank.com> (raw)
In-Reply-To: <50FF098C.8050707@profihost.ag>
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.
Mark
next prev parent reply other threads:[~2013-01-22 21:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-22 19:59 Questions about journals, performance and disk utilization martin
2013-01-22 21:16 ` Mark Nelson
2013-01-22 21:26 ` Jeff Mitchell
2013-01-22 21:50 ` Stefan Priebe
2013-01-22 21:56 ` Jeff Mitchell
2013-01-22 21:58 ` Stefan Priebe
2013-01-22 21:57 ` Mark Nelson [this message]
2013-01-22 21:58 ` Jeff Mitchell
2013-01-23 0:25 ` Josh Durgin
2013-01-23 2:23 ` Jeff Mitchell
2013-01-22 22:00 ` Gregory Farnum
2013-01-22 22:11 ` Mark Nelson
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