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Nov 21, 2025
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ceph: document client version bump and known issues #1991

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ceph: document bumping minimum client version
priteau Nov 21, 2025
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ceph: document known issues for Squid
priteau Nov 21, 2025
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46 changes: 46 additions & 0 deletions doc/source/operations/upgrading-ceph.rst
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Expand Up @@ -9,6 +9,37 @@ The Ceph release series is not strictly dependent upon the StackHPC OpenStack
release, however this configuration does define a default Ceph release series
and container image tag. The default release series is currently |ceph_series|.

Known issues
============

Slow ceph-volume activate
-------------------------

A large slowdown of ``ceph-volume activate`` has been reported on version
19.2.3 (`bug 73107 <https://tracker.ceph.com/issues/73107>`__).

On Reef, a host with 15 OSDs was measured taking around 10 seconds to activate
all OSDs while exiting maintenance mode. On Squid 19.2.3, a host with 22 OSDs
was measured taking 2 minutes to activate all OSDs.

This bug may be a blocker for deployments with large number of OSDs per host.

Elastic Shared Blob crash
-------------------------

There is a `known bug causing OSDs created on Squid to crash
<https://tracker.ceph.com/issues/70390>`__. To avoid it, `disable the
Elastic Shared Blob feature
<https://docs.clyso.com/blog/#squid-deployed-osds-are-crashing>`__ before
any OSDs are created or replaced:

.. code-block:: bash

ceph config set osd bluestore_elastic_shared_blobs 0

This needs to be done after the upgrade is complete as the option is not
available on Reef.

Prerequisites
=============

Expand Down Expand Up @@ -171,6 +202,21 @@ versions``. Once confirmed, run the following command:

ceph config set osd bluestore_elastic_shared_blobs 0

Finally, verify the value of ``ceph osd get-require-min-compat-client``. On
older Ceph deployments, it may still be set to ``jewel``, which would prevent
using the `upmap balancer mode
<https://docs.ceph.com/en/latest/rados/operations/balancer/#modes>`__ which
requires ``luminous`` or later. Similarly, the more recent `read balancer
<https://docs.ceph.com/en/latest/rados/operations/read-balancer/>`__ requires
``reef``.

Run ``ceph features`` to identify client versions and consider setting the
minimum to an appropriate value:

.. code-block:: console

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

Upgrade Cephadm
===============

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