Provided by: ceph-base_19.2.1-0ubuntu0.24.04.2_amd64 
NAME
osdmaptool - ceph osd cluster map manipulation tool
SYNOPSIS
osdmaptool mapfilename [--print] [--createsimple numosd
[--pgbits bitsperosd ] ] [--clobber]
osdmaptool mapfilename [--import-crush crushmap]
osdmaptool mapfilename [--export-crush crushmap]
osdmaptool mapfilename [--upmap file] [--upmap-max max-optimizations]
[--upmap-deviation max-deviation] [--upmap-pool poolname]
[--save] [--upmap-active]
osdmaptool mapfilename [--upmap-cleanup] [--upmap file]
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. It can also simulate the upmap balancer mode so you can get a sense of what is needed to balance
your PGs.
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).
--mark-out
mark an osd as out (but do not persist)
--mark-up <osdid>
mark an osd as up (but do not persist)
--mark-in <osdid>
mark an osd as in (but do not persist)
--tree Displays a hierarchical tree of the map.
--clear-temp
clears pg_temp and primary_temp variables.
--clean-temps
clean pg_temps.
--health
dump health checks
--with-default-pool
include default pool when creating map
--upmap-cleanup <file>
clean up pg_upmap[_items] entries, writing commands to <file> [default: - for stdout]
--upmap <file>
calculate pg upmap entries to balance pg layout writing commands to <file> [default: - for stdout]
--upmap-max <max-optimizations>
set max upmap entries to calculate [default: 10]
--upmap-deviation <max-deviation>
max deviation from target [default: 5]
--upmap-pool <poolname>
restrict upmap balancing to 1 pool or the option can be repeated for multiple pools
--upmap-active
Act like an active balancer, keep applying changes until balanced
--adjust-crush-weight <osdid:weight>[,<osdid:weight>,<...>]
Change CRUSH weight of <osdid>
--save write modified osdmap with upmap or crush-adjust changes
--read <file>
calculate pg upmap entries to balance pg primaries
--read-pool <poolname>
specify which pool the read balancer should adjust
--vstart
prefix upmap and read output with './bin/'
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 1:
osdmaptool osdmap --test-map-pgs-dump --pool 1
pool 1 pg_num 8
1.0 [0,2,1] 0
1.1 [2,0,1] 2
1.2 [0,1,2] 0
1.3 [2,0,1] 2
1.4 [0,2,1] 0
1.5 [0,2,1] 0
1.6 [0,1,2] 0
1.7 [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 1 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
• average, 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
To simulate the active balancer in upmap mode:
osdmaptool --upmap upmaps.out --upmap-active --upmap-deviation 6 --upmap-max 11 osdmap
osdmaptool: osdmap file 'osdmap'
writing upmap command output to: upmaps.out
checking for upmap cleanups
upmap, max-count 11, max deviation 6
pools movies photos metadata data
prepared 11/11 changes
Time elapsed 0.00310404 secs
pools movies photos metadata data
prepared 11/11 changes
Time elapsed 0.00283402 secs
pools data metadata movies photos
prepared 11/11 changes
Time elapsed 0.003122 secs
pools photos metadata data movies
prepared 11/11 changes
Time elapsed 0.00324372 secs
pools movies metadata data photos
prepared 1/11 changes
Time elapsed 0.00222609 secs
pools data movies photos metadata
prepared 0/11 changes
Time elapsed 0.00209916 secs
Unable to find further optimization, or distribution is already perfect
osd.0 pgs 41
osd.1 pgs 42
osd.2 pgs 42
osd.3 pgs 41
osd.4 pgs 46
osd.5 pgs 39
osd.6 pgs 39
osd.7 pgs 43
osd.8 pgs 41
osd.9 pgs 46
osd.10 pgs 46
osd.11 pgs 46
osd.12 pgs 46
osd.13 pgs 41
osd.14 pgs 40
osd.15 pgs 40
osd.16 pgs 39
osd.17 pgs 46
osd.18 pgs 46
osd.19 pgs 39
osd.20 pgs 42
Total time elapsed 0.0167765 secs, 5 rounds
To simulate the active balancer in read mode, first make sure capacity is balanced by running the
balancer in upmap mode. Then, balance the reads on a replicated pool with:
osdmaptool osdmap --read read.out --read-pool <pool name>
./bin/osdmaptool: osdmap file 'om'
writing upmap command output to: read.out
---------- BEFORE ------------
osd.0 | primary affinity: 1 | number of prims: 3
osd.1 | primary affinity: 1 | number of prims: 10
osd.2 | primary affinity: 1 | number of prims: 3
read_balance_score of 'cephfs.a.meta': 1.88
---------- AFTER ------------
osd.0 | primary affinity: 1 | number of prims: 5
osd.1 | primary affinity: 1 | number of prims: 5
osd.2 | primary affinity: 1 | number of prims: 6
read_balance_score of 'cephfs.a.meta': 1.13
num changes: 5
AVAILABILITY
osdmaptool 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),
COPYRIGHT
2010-2025, Inktank Storage, Inc. and contributors. Licensed under Creative Commons Attribution Share
Alike 3.0 (CC-BY-SA-3.0)
dev Jun 24, 2025 OSDMAPTOOL(8)