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