Hi Paul,

thanks for the fast reply. When you say "bit 21", do you mean "(feature_map & 
2^21) == true" (i.e., counting from 0 starting at the right-hand end)? Then it 
would be set for all connected ceph fs clients.

Assuming upmap is supported by all clients. If I understand correctly, to use 
the upmap mode with balancer, I need to set

ceph osd set-require-min-compat-client luminous

Which I would guess will not allow the jewel clients to reconnect. I would be 
grateful if you could clarify these points to me:

1) Can I use up-map mode without setting this?
2) If so, what happens if a jewel client without this feature bit set tries to 
connect?
3) I guess that in case that as soon as an up-map table is created, only 
clients with this bit set can connect. In case we run into problems, is there a 
way to roll back?

Many thanks and best regards,

=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14

________________________________________
From: Paul Emmerich <paul.emmer...@croit.io>
Sent: 13 April 2020 13:32:40
To: Frank Schilder
Cc: ceph-users
Subject: Re: [ceph-users] Check if upmap is supported by client?

bit 21 in the features bitmap is upmap support

Paul

--
Paul Emmerich

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On Mon, Apr 13, 2020 at 11:53 AM Frank Schilder <fr...@dtu.dk> wrote:
>
> Dear all,
>
> I would like to enable the balancer on a mimic 13.2.8 cluster in upmap mode. 
> Unfortunately, I have a lot of ceph fs kernel clients that report their 
> version as jewel, but might already support upmap. The ceph client kernel 
> module received already a lot of back-ports and supports features of later 
> ceph versions, for example, quotas. I guess they report back jewel, because 
> not all luminous/mimic features are back-ported yet. Is there a way to check 
> if a client supports upmap?
>
> Here some info:
>
> [root@gnosis ~]# ceph features
> {
>     [...]
>      "client": [
>         {
>             "features": "0x27018fb86aa42ada",
>             "release": "jewel",
>             "num": 1676
>         },
>         {
>             "features": "0x2f018fb86aa42ada",
>             "release": "luminous",
>             "num": 1
>         },
>         {
>             "features": "0x3ffddff8ffacfffb",
>             "release": "luminous",
>             "num": 167
>         }
>     ],
>
> The fs clients are the top two entries, the third entry is rbd clients. Note 
> that the feature key for the fs clients is almost identical. Here a snippet 
> from mds session ls for one such jewel client:
>
>     {
>         "id": 25641514,
>         "num_leases": 0,
>         "num_caps": 1,
>         "state": "open",
>         "request_load_avg": 0,
>         "uptime": 588563.550276,
>         "replay_requests": 0,
>         "completed_requests": 0,
>         "reconnecting": false,
>         "inst": "client.25641514 192.168.57.124:0/3398308464",
>         "client_metadata": {
>             "features": "00000000000000ff",
>             "entity_id": "con-fs2-hpc",
>             "hostname": "sn253.hpc.ait.dtu.dk",
>             "kernel_version": "3.10.0-957.12.2.el7.x86_64",
>             "root": "/hpc/groups"
>         }
>     }
>
> Since I would like to use upmap right from the beginning, my alternative is 
> to re-weight a few of the really bad outliers manually to simplify changing 
> back.
>
> What would you suggest?
>
> Thanks and best regards,
>
> =================
> Frank Schilder
> AIT Risø Campus
> Bygning 109, rum S14
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