osdmaptool – ceph osd cluster map manipulation tool

Synopsis

osdmaptool mapfilename [–print] [–createsimple numosd [–pgbits bitsperosd ] ] [–clobber]

Description

osdmaptool is a utility that lets you create, view, and manipulate OSD cluster maps from the Ceph distributed storage system. Notably, it lets you extract the embedded CRUSH map or import a new CRUSH map.

Options

--print

will simply make the tool print a plaintext dump of the map, after any modifications are made.

--dump <format>

displays the map in plain text when <format> is ‘plain’, ‘json’ if specified format is not supported. This is an alternative to the print option.

--clobber

will allow osdmaptool to overwrite mapfilename if changes are made.

--import-crush mapfile

will load the CRUSH map from mapfile and embed it in the OSD map.

--export-crush mapfile

will extract the CRUSH map from the OSD map and write it to mapfile.

--createsimple numosd [--pg-bits bitsperosd] [--pgp-bits bits]

will create a relatively generic OSD map with the numosd devices. If –pg-bits is specified, the initial placement group counts will be set with bitsperosd bits per OSD. That is, the pg_num map attribute will be set to numosd shifted by bitsperosd. If –pgp-bits is specified, then the pgp_num map attribute will be set to numosd shifted by bits.

--create-from-conf

creates an osd map with default configurations.

--test-map-pgs [--pool poolid] [--range-first <first> --range-last <last>]

will print out the mappings from placement groups to OSDs. If range is specified, then it iterates from first to last in the directory specified by argument to osdmaptool. Eg: osdmaptool –test-map-pgs –range-first 0 –range-last 2 osdmap_dir. This will iterate through the files named 0,1,2 in osdmap_dir.

--test-map-pgs-dump [--pool poolid] [--range-first <first> --range-last <last>]

will print out the summary of all placement groups and the mappings from them to the mapped OSDs. If range is specified, then it iterates from first to last in the directory specified by argument to osdmaptool. Eg: osdmaptool –test-map-pgs-dump –range-first 0 –range-last 2 osdmap_dir. This will iterate through the files named 0,1,2 in osdmap_dir.

--test-map-pgs-dump-all [--pool poolid] [--range-first <first> --range-last <last>]

will print out the summary of all placement groups and the mappings from them to all the OSDs. If range is specified, then it iterates from first to last in the directory specified by argument to osdmaptool. Eg: osdmaptool –test-map-pgs-dump-all –range-first 0 –range-last 2 osdmap_dir. This will iterate through the files named 0,1,2 in osdmap_dir.

--test-random

does a random mapping of placement groups to the OSDs.

--test-map-pg <pgid>

map a particular placement group(specified by pgid) to the OSDs.

--test-map-object <objectname> [--pool <poolid>]

map a particular placement group(specified by objectname) to the OSDs.

--test-crush [--range-first <first> --range-last <last>]

map placement groups to acting OSDs. If range is specified, then it iterates from first to last in the directory specified by argument to osdmaptool. Eg: osdmaptool –test-crush –range-first 0 –range-last 2 osdmap_dir. This will iterate through the files named 0,1,2 in osdmap_dir.

--mark-up-in

mark osds up and in (but do not persist).

--tree

Displays a hierarchical tree of the map.

--clear-temp

clears pg_temp and primary_temp variables.

Example

To create a simple map with 16 devices:

osdmaptool --createsimple 16 osdmap --clobber

To view the result:

osdmaptool --print osdmap

To view the mappings of placement groups for pool 0:

osdmaptool --test-map-pgs-dump rbd --pool 0

pool 0 pg_num 8
0.0     [0,2,1] 0
0.1     [2,0,1] 2
0.2     [0,1,2] 0
0.3     [2,0,1] 2
0.4     [0,2,1] 0
0.5     [0,2,1] 0
0.6     [0,1,2] 0
0.7     [1,0,2] 1
#osd    count   first   primary c wt    wt
osd.0   8       5       5       1       1
osd.1   8       1       1       1       1
osd.2   8       2       2       1       1
 in 3
 avg 8 stddev 0 (0x) (expected 2.3094 0.288675x))
 min osd.0 8
 max osd.0 8
size 0  0
size 1  0
size 2  0
size 3  8
In which,
  1. pool 0 has 8 placement groups. And two tables follow:
  2. A table for placement groups. Each row presents a placement group. With columns of:
    • placement group id,
    • acting set, and
    • primary OSD.
  3. A table for all OSDs. Each row presents an OSD. With columns of:
    • count of placement groups being mapped to this OSD,
    • count of placement groups where this OSD is the first one in their acting sets,
    • count of placement groups where this OSD is the primary of them,
    • the CRUSH weight of this OSD, and
    • the weight of this OSD.
  4. Looking at the number of placement groups held by 3 OSDs. We have
    • avarge, stddev, stddev/average, expected stddev, expected stddev / average
    • min and max
  5. The number of placement groups mapping to n OSDs. In this case, all 8 placement groups are mapping to 3 different OSDs.

In a less-balanced cluster, we could have following output for the statistics of placement group distribution, whose standard deviation is 1.41421:

#osd    count   first   primary c wt    wt
osd.0   8       5       5       1       1
osd.1   8       1       1       1       1
osd.2   8       2       2       1       1

#osd    count   first    primary c wt    wt
osd.0   33      9        9       0.0145874     1
osd.1   34      14       14      0.0145874     1
osd.2   31      7        7       0.0145874     1
osd.3   31      13       13      0.0145874     1
osd.4   30      14       14      0.0145874     1
osd.5   33      7        7       0.0145874     1
 in 6
 avg 32 stddev 1.41421 (0.0441942x) (expected 5.16398 0.161374x))
 min osd.4 30
 max osd.1 34
size 00
size 10
size 20
size 364

Availability

osdmaptool is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to the Ceph documentation at http://ceph.com/docs for more information.

See also

ceph(8), crushtool(8),