>
> Helllo,
>
> I've reviewed some recent posts in this list and also searched Google for
> info about autoscale and overlapping roots. In what I have found I do not
> see anything that I can understand regarding how to fix the issue -
> probably because I don't deal with Crush on a regular basis.
Checkout the Note in this section:
https://docs.ceph.com/en/reef/rados/operations/placement-groups/#viewing-pg-scaling-recommendations
I added that last year I think it was as a result of how Rook was creating
pools.
>
> From what I read and looking at 'ceph osd crush rule dump', it looks like
> the 8 replicated pools have
>
> "op": "take",
> "item": -1,
> "item_name": "default"
>
> whereas the 2 EC pools have
>
> "op": "take",
> "item": -2,
> "item_name": "default~hdd"
>
> To be sure, all of my OSDs are identical - HDD with SSD WAL/DB.
>
> Please advise on how to fix this.
The subtlety that's easy to miss is that when you specify a device class for
only *some* pools, the pools/rules that specify a device class effectively act
on a "shadow" CRUSH root. My terminology may be inexact there.
So I think if you adjust your CRUSH rules so that they all specify a device
class -- in your case all the same device class -- your problem (and balancer
performance perhaps) will improve.
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