Re: Is there any way to fine tune peering/pg relocation/rebalance?

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Seems like tested on nautilus but I still see commits last month so I guess it is good with octopus.

________________________________
From: Matt Vandermeulen <storage@xxxxxxxxxxxx>
Sent: Wednesday, August 30, 2023 12:44 AM
To: Szabo, Istvan (Agoda) <Istvan.Szabo@xxxxxxxxx>
Cc: Ceph Users <ceph-users@xxxxxxx>
Subject: Re:  Is there any way to fine tune peering/pg relocation/rebalance?

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________________________________

We have had success using pgremapper[1] for this sort of thing, in both
index and data augments.

1. Set nobackfill, norebalance
2. Add OSDs
3. pgremapper cancel-backfill
4. Unset flags
5. Slowly loop `pgremapper undo-upmaps` at our desired rate, or allow
the balancer to do this work

There's still going to be the hit from peering, especially when you
change the CRUSH map (before even bringing the OSDs in), but in general
peering has been very quick for us for the last few releases, and s3 has
enough overhead where it's not overly noticed.  We haven't done multiple
OSDs per device, however, and have plenty CPU power.

[1] https://github.com/digitalocean/pgremapper



On 2023-08-29 17:51, Szabo, Istvan (Agoda) wrote:
> Hello,
>
> Is there a way to somehow fine tune the rebalance even further than
> basic tuning steps when adding new osds?
> Today I've added some osd to the index pool and it generated many slow
> ops due to OSD op latency increase + read operation latency increase =
> high put get latency.
>
> https://ibb.co/album/9mN6GQ
>
> osd max backfill, max recovery, recovery ops priority are 1.
> 1 nvme drive has 4 osd, each osd has around 80pg.
>
> The steps how I add the osds:
>
>   1.  Set norebalance
>   2.  add the osds
>   3.  wait for peering
>   4.  unset rebalance
>
> It takes like 15-20 mins to became normal without interrupting the
> rebalance the user traffic.
>
> Thank you,
> Istvan
>
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