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:orphan:
.. _crushdiff:
=======================================
crushdiff -- ceph crush map test tool
=======================================
.. program:: crushdiff
Synopsis
========
| **crushdiff** [ --osdmap *osdmap* ] [ --pg-dump *pg-dump* ]
[ --compiled ] [ --verbose ] *command* *crushmap*
Description
===========
**crushdiff** is a utility that lets you test the effect of a crushmap
change: number of pgs, objects, bytes moved. This is a wrapper around
:doc:`osdmaptool <osdmaptool>`\(8), relying on its **--test-map-pgs-dump**
option to get the list of changed pgs. Additionally it uses pg stats
to calculate the numbers of objects and bytes moved.
By default, **crushdiff** will use the cluster current osdmap and pg
stats, which requires access to the cluster. Though one can use the
**--osdmap** and **--pg-dump** options to test against previously
obtained data.
Options
=======
.. option:: --compiled
The input/output crushmap is compiled. If the options is not
specified the expected/returned crushmap is in txt (decompiled)
format.
.. option:: --pg-dump <pg-dump>
JSON output of **ceph pg dump**. If not specified **crushdiff**
will try to get data running the command itself.
.. option:: --osdmap <osdmap>
The cluster osdmap, obtained with **ceph osd getmap** command. If
not specified **crushdiff** will try to get data running the
command itself.
.. option:: --verbose
Produce diagnostic output.
Commands
========
:command:`compare` *crushmap*
Compare the crushmap from *crushmap* file with the crushmap from
the cluster osdmap. The output will show the expected number of pgs,
objects, bytes moved when the new crushmap is installed.
:command:`export` *crushmap*
Export crushmap to *crushmap* file from the cluster osdmap.
:command:`import` *crushmap*
Import crushmap from *crushmap* file to the cluster osdmap.
Example
=======
Get the current crushmap::
crushdiff export cm.txt
Edit the map::
$EDITOR cm.txt
Check the result::
crushdiff compare cm.txt
79/416 (18.99%) pgs affected
281/1392 (20.19%) objects affected
80/1248 (6.41%) pg shards to move
281/4176 (6.73%) pg object shards to move
730.52Mi/10.55Gi (6.76%) bytes to move
When running with **--verbose** option the output will also contain
detailed information about the affected pgs, like below::
4.3 [0, 2, 1] -> [1, 4, 2]
4.b [0, 1, 3] -> [2, 1, 3]
4.c [4, 0, 1] -> [4, 1, 2]
i.e. a pg number, and its old and the new osd active sets.
If the result is satisfactory install the updated map::
crushdiff import cm.txt
Availability
============
**crushdiff** is part of Ceph, a massively scalable, open-source, distributed storage system. Please
refer to the Ceph documentation at https://docs.ceph.com for more
information.
See also
========
:doc:`ceph <ceph>`\(8),
:doc:`crushtool <crushtool>`\(8),
:doc:`osdmaptool <osdmaptool>`\(8),
|
