Hi Brian and Robert,
Thanks for your replies! Appreciate.
Can I safely say that there will be no downtime to the cluster when I increase the pg_num and pgp_num values?Thanks for your replies! Appreciate.
Looking forward to your reply, thank you.
Cheers.
Cheers.
On Tue, Dec 3, 2013 at 2:31 PM, Robert van Leeuwen <Robert.vanLeeuwen@xxxxxxxxxxxxx> wrote:
> On 2 dec. 2013, at 18:26, "Brian Andrus" <brian.andrus@xxxxxxxxxxx> wrote:
> Setting your pg_num and pgp_num to say... 1024 would A) increase data granularity, B) likely lend no noticeable increase to resource consumption, and C) allow some room for future OSDs two be added while still within range of acceptable pg numbers. You could probably safely double even that number if you plan on expanding at a rapid rate and want to avoid splitting PGs every time a node is added.
>I would be a bit conservative with the PGs / PGPs.
> In general, you can conservatively err on the larger side when it comes to pg/p_num. Any excess resource utilization will be negligible (up to a certain point). If you have a comfortable amount of available RAM, you could experiment with increasing the multiplier in the equation you are using and see how it affects your final number.
>
> The pg_num and pgp_num parameters can safely be changed before or after your new nodes are integrated.
I've experimented with the PG number a bit and noticed the following random IO performance drop.
( this could be something to our specific setup but since the PG is easily increased and impossible to decrease I would be conservative)
The setup:
3 OSD nodes with 128GB ram, 2 * 6 core CPU (12 with ht).
Nodes have 10 OSDs running on 1 tb disks and 2 SSDs for Journals.
We use a replica count of 3 so optimum according to formula is about 1000
With 1000 PGs I got about 2000-2500 random 4k IOPS.
Because the nodes are fast enough and I expect the cluster to be expanded with 3 more nodes I set the PGs to 2000.
Performance dropped to about 1200-1400 IOPS.
I noticed that the spinning disks where no longer maxing out on 100% usage.
Memory and CPU did not seem to be a problem.
Since had the option to recreate the pool and I was not using the recommended settings I did not really dive into the issue.
I will not stray to far from the recommended settings in the future though :)
Cheers,
Robert van Leeuwen
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