Ceph » RADOS

The individual config parameters related to reservation
weight and limit are not modifiable during runtime when
a built-in profile is active.

But when the 'custom' profile is active, it must be
possible for an user to modify the above parameters using
the "config set" and other commands during runtime.

This is related to the issue reported in the ceph-user
community:

https://lists.ceph.io/hyperkitty/list/ceph-users@ceph.io/thread/KBCSQWMWTQOH3TZ65R4PIXVNRYGNP77D/

This will require changes in the mClockScheduler and may
be in the Ceph config subsystem.

Workaround

Until a fix is available, the following workaround may be used
to override the parameters:

1. Run the injectargs command as shown in the following example
to override the mclock settings.

$ ceph tell osd.0 injectargs '--osd_mclock_scheduler_background_recovery_res=10'

OR

2. Another alternative command you could use is:

$ ceph daemon osd.0 config set osd_mclock_scheduler_background_recovery_res 10

3. The above settings are ephemeral and are lost in case the
OSD restarts. To ensure that the above values are retained
after an OSD restarts, run the following additional command,

$ ceph config set osd.0 osd_mclock_scheduler_background_recovery_res 10

The above steps must be followed for any subsequent change to
the mclock config parameters when using the 'custom' profile.