How many PGs in each OSD of a Ceph cluster ?

To display how many PGs in each OSD of a Ceph cluster:

$ ceph --format xml pg dump | \
   xmlstarlet sel -t -m "//pg_stats/pg_stat/acting" -v osd -n | \
   sort -n | uniq -c
    332 0
    312 1
    299 2
    326 3
    291 4
    295 5
    316 6
    311 7
    301 8
    313 9

Where xmlstarlet loops over each PG acting set ( -m “//pg_stats/pg_stat/acting” ) and displays the OSDs it contains (-v osd), one by line (-n). The first column is the number of PGs in which the OSD in the second column shows.
To restrict the display to the PGs belonging to a given pool:

ceph --format xml pg dump |  \
  xmlstarlet sel -t -m "//pg_stats/pg_stat[starts-with(pgid,'0.')]/acting" -v osd -n | \
  sort -n | uniq -c

Where 0. is the prefix of each PG that belongs to pool 0.

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3 Responses to How many PGs in each OSD of a Ceph cluster ?

  1. Salut Loïc,

    Did you try to run the same command but instead of the whole cluster on pool basis?
    Would be nice to check the distribution for certain pool too ;-) .
    Thanks!

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