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.