Hi Frank, thanks this 'root default' indeed looks different with these 0 there. I have also uploaded mine[1] because it looks very similar to Nico's. I guess his hdd pg's can also start moving in some occassions. Thanks for 'crushtool reclassify' hint, I guess I have missed this in the release notes or so. [1] https://pastebin.com/PFx0V3S7 -----Original Message----- To: Eugen Block Cc: Marc Roos; ceph-users Subject: Re: [ceph-users] Re: hdd pg's migrating when converting ssd class osd's This is how my crush tree including shadow hierarchies looks like (a mess :): https://pastebin.com/iCLbi4Up Every device class has its own tree. Starting with mimic, this is automatic when creating new device classes. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Eugen Block <eblock@nde.ag> Sent: 30 September 2020 08:43:47 To: Frank Schilder Cc: Marc Roos; ceph-users Subject: Re: [ceph-users] Re: hdd pg's migrating when converting ssd class osd's Interesting, I also did this test on an upgraded cluster (L to N). I'll repeat the test on a native Nautilus to see it for myself. Zitat von Frank Schilder
Somebody on this list posted a script that can convert pre-mimic crush
trees with buckets for different types of devices to crush trees with device classes with minimal data movement (trying to maintain IDs as much as possible). Don't have a thread name right now, but could try to find it tomorrow.
I can check tomorrow how our crush tree unfolds. Basically, for every device class there is a full copy (shadow hierarchy) for each device class with its own weights etc.
Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14
________________________________________ From: Marc Roos Sent: 29 September 2020 22:19:33 To: eblock; Frank Schilder Cc: ceph-users Subject: RE: [ceph-users] Re: hdd pg's migrating when converting ssd class osd's
Yes correct this is coming from Luminous or maybe even Kraken. How does a default crush tree look like in mimic or octopus? Or is there some manual how to bring this to the new 'default'?
-----Original Message----- Cc: ceph-users Subject: Re: [ceph-users] Re: hdd pg's migrating when converting ssd class osd's
Are these crush maps inherited from pre-mimic versions? I have re-balanced SSD and HDD pools in mimic (mimic deployed) where one device class never influenced the placement of the other. I have mixed
hosts and went as far as introducing rbd_meta, rbd_data and such classes to sub-divide even further (all these devices have different perf specs). This worked like a charm. When adding devices of one class, only pools
in this class were ever affected.
As far as I understand, starting with mimic, every shadow class defines a separate tree (not just leafs/OSDs). Thus, device classes are independent of each other.
________________________________________ Sent: 29 September 2020 20:54:48 To: eblock Cc: ceph-users Subject: [ceph-users] Re: hdd pg's migrating when converting ssd class
osd's
Yes correct, hosts have indeed both ssd's and hdd's combined. Is this not more of a bug then? I would assume the goal of using device classes is that you separate these and one does not affect the other, even the host weight of the ssd and hdd class are already available. The algorithm should just use that instead of the weight of the whole host. Or is there some specific use case, where these classes combined is required?
-----Original Message----- Cc: ceph-users Subject: *****SPAM***** Re: [ceph-users] Re: hdd pg's migrating when converting ssd class osd's
They're still in the same root (default) and each host is member of both device-classes, I guess you have a mixed setup (hosts c01/c02 have both HDDs and SSDs)? I don't think this separation is enough to avoid remapping even if a different device-class is affected (your report confirms that).
Dividing the crush tree into different subtrees might help here but I'm not sure if that's really something you need. You might also just deal with the remapping as long as it doesn't happen too often, I guess. On the other hand, if your setup won't change (except adding more OSDs) you might as well think about a different crush tree. It really depends on your actual requirements.
We created two different subtrees when we got new hardware and it helped us a lot moving the data only once to the new hardware avoiding
multiple remappings, now the older hardware is our EC environment except for some SSDs on those old hosts that had to stay in the main subtree. So our setup is also very individual but it works quite nice. :-)
Zitat von :
I have practically a default setup. If I do a 'ceph osd crush tree --show-shadow' I have a listing like this[1]. I would assume from the
hosts being listed within the default~ssd and default~hdd, they are separate (enough)?
[1] root default~ssd host c01~ssd .. .. host c02~ssd .. root default~hdd host c01~hdd .. host c02~hdd .. root default
-----Original Message----- To: ceph-users@ceph.io Subject: [ceph-users] Re: hdd pg's migrating when converting ssd class
osd's
Are all the OSDs in the same crush root? I would think that since the
crush weight of hosts change as soon as OSDs are out it impacts the whole crush tree. If you separate the SSDs from the HDDs logically (e.g. different bucket type in the crush tree) the ramapping wouldn't affect
the HDDs.
I have been converting ssd's osd's to dmcrypt, and I have noticed that
pg's of pools are migrated that should be (and are?) on hdd class.
On a healthy ok cluster I am getting, when I set the crush reweight to
0.0 of a ssd osd this:
17.35 10415 0 0 9907 0 36001743890 0 0 3045 3045 active+remapped+backfilling 2020-09-27 12:55:49.093054 active+remapped+83758'20725398 83758:100379720 [8,14,23] 8 [3,14,23] 3 83636'20718129 2020-09-27 00:58:07.098096 83300'20689151 2020-09-24 21:42:07.385360 0
However osds 3,14,23,8 are all hdd osd's
Since this is a cluster from Kraken/Luminous, I am not sure if the device class of the replicated_ruleset[1] was set when the pool 17 was
created. Weird thing is that all pg's of this pool seem to be on hdd osd[2]
Q. How can I display the definition of 'crush_rule 0' at the time of
the pool creation? (To be sure it had already this device class hdd configured)
[1] [@~]# ceph osd pool ls detail | grep 'pool 17' pool 17 'rbd' replicated size 3 min_size 2 crush_rule 0 object_hash rjenkins pg_num 64 pgp_num 64 autoscale_mode warn last_change 83712 flags hashpspool,selfmanaged_snaps stripe_width 0 application rbd
[@~]# ceph osd crush rule dump replicated_ruleset { "rule_id": 0, "rule_name": "replicated_ruleset", "ruleset": 0, "type": 1, "min_size": 1, "max_size": 10, "steps": [ { "op": "take", "item": -10, "item_name": "default~hdd" }, { "op": "chooseleaf_firstn", "num": 0, "type": "host" }, { "op": "emit" } ] }
[2] [@~]# for osd in `ceph pg dump pgs| grep '^17' | awk '{print $17" "$19}' | grep -oE '[0-9]{1,2}'| sort -u -n`; do ceph osd crush | get-device-class osd.$osd ; done | sort -u dumped pgs hdd
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