From: Xiaopong Tran <xiaopong.tran@gmail.com>
To: Anders Saaby <anders@saaby.com>
Cc: Wido den Hollander <wido@42on.com>,
"ceph-devel@vger.kernel.org" <ceph-devel@vger.kernel.org>
Subject: Re: placement group sizing
Date: Sat, 27 Apr 2013 12:45:11 +0800 [thread overview]
Message-ID: <517B57D7.8080306@gmail.com> (raw)
In-Reply-To: <BE9322CA-90F7-4D71-9EB0-6FD7FA61E4AD@saaby.com>
On 04/27/2013 01:07 AM, Anders Saaby wrote:
>
>> How many OSDs per machine do you have and how much memory do you have per machine?
>
> 12 OSD's per machine. A bit over 1GB memory per OSD. (16GB per machine)
>
Try more. If you have a large-ish cluster, with many OSDs, and if you
have large PGs, when one or more OSDs go down (for different reasons,
a crash, a disk failure, etc), Ceph will start to remap and rebalance,
memory usage per OSD can easily balloon to GBs per OSD.
When this happens, and if you don't have enough memory, the
OSD processes might get OOM-killed, and you'll get into a
vicious cycle.
>> The more PGs you have, the more peering PGs you will have when an OSD boots again, so that could be heavy for the CPU in the machines.
>
> Right.
>
next prev parent reply other threads:[~2013-04-27 4:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-25 12:39 placement group sizing Anders Saaby
2013-04-26 12:22 ` Wido den Hollander
2013-04-26 17:07 ` Anders Saaby
2013-04-27 4:45 ` Xiaopong Tran [this message]
2013-04-29 7:17 ` Anders Saaby
2013-04-26 13:17 ` Mark Nelson
2013-04-26 17:09 ` Anders Saaby
-- strict thread matches above, loose matches on Subject: below --
2013-04-25 12:36 Anders Saaby
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