[ceph-users] Check if upmap is supported by client?

13 Apr 2020

      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