mirror of
https://github.com/ceph/ceph
synced 2024-12-21 02:42:48 +00:00
76 lines
2.7 KiB
ReStructuredText
76 lines
2.7 KiB
ReStructuredText
Using the pg-upmap
|
|
==================
|
|
|
|
Starting in Luminous v12.2.z there is a new *pg-upmap* exception table
|
|
in the OSDMap that allows the cluster to explicitly map specific PGs to
|
|
specific OSDs. This allows the cluster to fine-tune the data
|
|
distribution to, in most cases, perfectly distributed PGs across OSDs.
|
|
|
|
The key caveat to this new mechanism is that it requires that all
|
|
clients understand the new *pg-upmap* structure in the OSDMap.
|
|
|
|
Enabling
|
|
--------
|
|
|
|
To allow use of the feature, you must tell the cluster that it only
|
|
needs to support luminous (and newer) clients with::
|
|
|
|
ceph osd set-require-min-compat-client luminous
|
|
|
|
This command will fail if any pre-luminous clients or daemons are
|
|
connected to the monitors. You can see what client versions are in
|
|
use with::
|
|
|
|
ceph features
|
|
|
|
A word of caution
|
|
-----------------
|
|
|
|
This is a new feature and not very user friendly. At the time of this
|
|
writing we are working on a new `balancer` module for ceph-mgr that
|
|
will eventually do all of this automatically.
|
|
|
|
Until then,
|
|
|
|
Offline optimization
|
|
--------------------
|
|
|
|
Upmap entries are updated with an offline optimizer built into ``osdmaptool``.
|
|
|
|
#. Grab the latest copy of your osdmap::
|
|
|
|
ceph osd getmap -o om
|
|
|
|
#. Run the optimizer::
|
|
|
|
osdmaptool om --upmap out.txt [--upmap-pool <pool>] [--upmap-max <max-count>] [--upmap-deviation <max-deviation>]
|
|
|
|
It is highly recommended that optimization be done for each pool
|
|
individually, or for sets of similarly-utilized pools. You can
|
|
specify the ``--upmap-pool`` option multiple times. "Similar pools"
|
|
means pools that are mapped to the same devices and store the same
|
|
kind of data (e.g., RBD image pools, yes; RGW index pool and RGW
|
|
data pool, no).
|
|
|
|
The ``max-count`` value is the maximum number of upmap entries to
|
|
identify in the run. The default is 100, but you may want to make
|
|
this a smaller number so that the tool completes more quickly (but
|
|
does less work). If it cannot find any additional changes to make
|
|
it will stop early (i.e., when the pool distribution is perfect).
|
|
|
|
The ``max-deviation`` value defaults to `.01` (i.e., 1%). If an OSD
|
|
utilization varies from the average by less than this amount it
|
|
will be considered perfect.
|
|
|
|
#. The proposed changes are written to the output file ``out.txt`` in
|
|
the example above. These are normal ceph CLI commands that can be
|
|
run to apply the changes to the cluster. This can be done with::
|
|
|
|
source out.txt
|
|
|
|
The above steps can be repeated as many times as necessary to achieve
|
|
a perfect distribution of PGs for each set of pools.
|
|
|
|
You can see some (gory) details about what the tool is doing by
|
|
passing ``--debug-osd 10`` to ``osdmaptool``.
|