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doc: Update mclock-config-ref doc steps to override osd max iops capa…
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…city.

Update the steps in the mclock config reference document to manually
override an OSDs max IOPS capacity. Provide information on the alternative
ways to override the osd_mclock_max_capacity_iops_[hdd,ssd] options for
an OSD.

Fixes: https://tracker.ceph.com/issues/52025
Signed-off-by: Sridhar Seshasayee <sseshasa@redhat.com>
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sseshasa committed Aug 3, 2021
1 parent 129efb8 commit 11881c6
Showing 1 changed file with 20 additions and 18 deletions.
38 changes: 20 additions & 18 deletions doc/rados/configuration/mclock-config-ref.rst
Expand Up @@ -151,14 +151,14 @@ command:

.. prompt:: bash #

ceph config set [global,osd] osd_mclock_profile <value>
ceph config set osd.N osd_mclock_profile <value>

For example, to change the profile to allow faster recoveries, the following
command can be used to switch to the *high_recovery_ops* profile:
For example, to change the profile to allow faster recoveries on "osd.0", the
following command can be used to switch to the *high_recovery_ops* profile:

.. prompt:: bash #

ceph config set osd osd_mclock_profile high_recovery_ops
ceph config set osd.0 osd_mclock_profile high_recovery_ops

.. note:: The *custom* profile is not recommended unless you are an advanced
user.
Expand All @@ -179,9 +179,9 @@ cluster is brought up by using the following command:

.. prompt:: bash #

ceph config show osd.x osd_mclock_max_capacity_iops_[hdd, ssd]
ceph config show osd.N osd_mclock_max_capacity_iops_[hdd, ssd]

For example, the following command shows the max capacity for osd.0 on a Ceph
For example, the following command shows the max capacity for "osd.0" on a Ceph
node whose underlying device type is SSD:

.. prompt:: bash #
Expand All @@ -196,6 +196,11 @@ Steps to Manually Benchmark an OSD (Optional)
capacity already determined automatically during OSD initialization.
Otherwise, you may skip this section entirely.

.. tip:: If you have already determined the benchmark data and wish to manually
override the max osd capacity for an OSD, you may skip to section
`Specifying Max OSD Capacity`_.


Any existing benchmarking tool can be used for this purpose. In this case, the
steps use the *Ceph OSD Bench* command described in the next section. Regardless
of the tool/command used, the steps outlined further below remain the same.
Expand Down Expand Up @@ -285,28 +290,25 @@ Specifying Max OSD Capacity
````````````````````````````

The steps in this section may be performed only if you want to override the
max osd capacity automatically determined during OSD initialization. The option
``osd_mclock_max_capacity_iops_[hdd, ssd]`` can be set by running the
max osd capacity automatically set during OSD initialization. The option
``osd_mclock_max_capacity_iops_[hdd, ssd]`` for an OSD can be set by running the
following command:

.. prompt:: bash #

ceph config set [global,osd] osd_mclock_max_capacity_iops_[hdd,ssd] <value>
ceph config set osd.N osd_mclock_max_capacity_iops_[hdd,ssd] <value>

For example, the following command sets the max capacity for all the OSDs in a
Ceph node whose underlying device type is SSDs:

.. prompt:: bash #

ceph config set osd osd_mclock_max_capacity_iops_ssd 25000

To set the capacity for a specific OSD (for example "osd.0") whose underlying
device type is HDD, use a command like this:
For example, the following command sets the max capacity for a specific OSD
(say "osd.0") whose underlying device type is HDD to 350 IOPS:

.. prompt:: bash #

ceph config set osd.0 osd_mclock_max_capacity_iops_hdd 350

Alternatively, you may specify the max capacity for OSDs within the Ceph
configuration file under the respective [osd.N] section. See
:ref:`ceph-conf-settings` for more details.


.. index:: mclock; config settings

Expand Down

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