NAME

       crushdiff - ceph crush map test tool

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  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

       --compiled
              The input/output crushmap  is  compiled.  If  the  options  is  not  specified  the
              expected/returned crushmap is in txt (decompiled) format.

       --pg-dump <pg-dump>
              JSON  output  of  ceph  pg  dump.  If  not specified crushdiff will try to get data
              running the command itself.

       --osdmap <osdmap>
              The cluster osdmap, obtained  with  ceph  osd  getmap  command.  If  not  specified
              crushdiff will try to get data running the command itself.

       --verbose
              Produce diagnostic output.

COMMANDS

       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.

       export crushmap
              Export crushmap to crushmap file from the cluster osdmap.

       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

       ceph(8), crushtool(8), osdmaptool(8),

COPYRIGHT

       2010-2022,  Inktank  Storage,  Inc.  and  contributors.  Licensed  under  Creative Commons
       Attribution Share Alike 3.0 (CC-BY-SA-3.0)