Provided by: ceph_0.41-1ubuntu2_amd64 bug

NAME

       crushtool - CRUSH map manipulation tool

SYNOPSIS

       crushtool ( -d map | -c map.txt | --build numosds
       layer1 ... ) [ -o outfile [ --clobber ]]

DESCRIPTION

       crushtool is a utility that lets you create, compile, and decompile CRUSH map files.

       CRUSH  is  a  pseudo-random data distribution algorithm that efficiently maps input values
       (typically data objects) across a heterogeneous, hierarchically structured device map. The
       algorithm  was  originally  described  in  detail  in the following paper (although it has
       evolved some since then):
          http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf

       The tool has three modes of operation.

       -c map.txt
              will compile a plaintext map.txt into a binary map file.

       -d map will take the compiled map and decompile it into a plaintext source file,  suitable
              for editing.

       --build numosds layer1 ...
              will  create a relatively generic map with the given layer structure. See below for
              examples.

OPTIONS

       -o outfile
              will specify the output file.

       --clobber
              will allow the tool to overwrite an existing outfile (it will normally refuse).

BUILDING A MAP

       The build mode will generate relatively generic  hierarchical  maps.  The  first  argument
       simply  specifies  the  number  of  devices  (leaves)  in  the CRUSH hierarchy. Each layer
       describes how the layer (or raw devices) preceding it should be grouped.

       Each layer consists of:

       name ( uniform | list | tree | straw ) size

       The first element is the name for the elements in the layer (e.g. "rack"). Each  element's
       name will be append a number to the provided name.

       The second component is the type of CRUSH bucket.

       The  third  component is the maximum size of the bucket. If the size is 0, a single bucket
       will be generated that includes everything in the preceding layer.

EXAMPLE

       Suppose we have 128 devices, each grouped into shelves with 4 devices each, and 8  shelves
       per rack. We could create a three level hierarchy with:

       crushtool --build 128 shelf uniform 4 rack straw 8 root straw 0 -o map

       To adjust the default (generic) mapping rules, we can run:

       # decompile
       crushtool -d map -o map.txt

       # edit
       vi map.txt

       # recompile
       crushtool -c map.txt -o map

AVAILABILITY

       crushtool  is  part  of the Ceph distributed file system. Please refer to the Ceph wiki at
       http://ceph.newdream.net/wiki for more information.

SEE ALSO

       ceph(8), osdmaptool(8), mkcephfs(8)

COPYRIGHT

       2011, New Dream Network