On 5 January 2015 at 14:20, Christian Balzer <chibi@xxxxxxx> wrote:
On Mon, 5 Jan 2015 14:04:28 +0400 ivan babrou wrote:
> Hi!
>
> I have a cluster with 106 osds and disk usage is varying from 166gb to
> 316gb. Disk usage is highly correlated to number of pg per osd (no
> surprise here). Is there a reason for ceph to allocate more pg on some
> nodes?
>
In essence what Wido said, you're a bit low on PGs.
Also given your current utilization, pool 14 is totally oversize with 1024
PGs. You might want to re-create it with a smaller size and double pool 0
to 512 PGs and 10 to 4096.
I assume you did raise the PGPs as well when changing the PGs, right?
Yep, pg = pgp for all pools. Pool 14 is just for testing purposes, it might get large eventually.
I followed you advice in doubling pools 0 and 10. It is rebalancing at 30% degraded now, but so far big osds become bigger and small become smaller: http://i.imgur.com/hJcX9Us.png. I hope that trend would change before rebalancing is complete.
And yeah, CEPH isn't particular good at balancing stuff by itself, but
with sufficient PGs you ought to get the variance below/around 30%.
Is this going to change in the future releases?
Christian
> The biggest osds are 30, 42 and 69 (300gb+ each) and the smallest are 87,
> 33 and 55 (170gb each). The biggest pool has 2048 pgs, pools with very
> little data has only 8 pgs. PG size in biggest pool is ~6gb (5.1..6.3
> actually).
>
> Lack of balanced disk usage prevents me from using all the disk space.
> When the biggest osd is full, cluster does not accept writes anymore.
>
> Here's gist with info about my cluster:
> https://gist.github.com/bobrik/fb8ad1d7c38de0ff35ae
>
--
Christian Balzer Network/Systems Engineer
chibi@xxxxxxx Global OnLine Japan/Fusion Communications
http://www.gol.com/
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