下記でMETA容量を下げる事ができる。

# ceph tell osd.<osd-id> compact 

※METAが多くなりすぎるとと、IO負荷が異常に高くなるので大きくなり過ぎる前に実行した方が良い。

# ceph tell osd.2 compact
{
    "elapsed_time": 6.5991835759999997
}

# ceph osd df tree | awk 'NR==1;NR>1{print $0|"sort -k 13 -r -n "} '
ID   CLASS  WEIGHT     REWEIGHT  SIZE     RAW USE  DATA     OMAP     META     AVAIL    %USE   VAR   PGS  STATUS  TYPE NAME            
  2    hdd    9.09569   1.00000  3.1 TiB  1.7 TiB  1.6 TiB  546 KiB  101 GiB  7.4 TiB  18.83  0.53   10      up          osd.2

# ceph osd df tree | awk 'NR==1;NR>1{print $0|"sort -k 13 -r -n "} '
ID   CLASS  WEIGHT     REWEIGHT  SIZE     RAW USE  DATA     OMAP     META     AVAIL    %USE   VAR   PGS  STATUS  TYPE NAME            
  2    hdd    9.09569   1.00000  3.1 TiB  1.7 TiB  1.6 TiB  546 KiB  1 GiB  7.4 TiB  18.83  0.53   10      up          osd.2

# ceph tell osd.0 perf dump | jq '.bluefs'
{
  "db_total_bytes": 1000079360000,
  "db_used_bytes": 567279616,
  "wal_total_bytes": 2663382630,
  "wal_used_bytes": 563399884,
  "slow_total_bytes": 0,
  "slow_used_bytes": 0,
  "num_files": 195,
  "log_bytes": 6828032,
  "log_compactions": 46526,
  "logged_bytes": 31066742784,
  "files_written_wal": 10459,
  "files_written_sst": 6928,
  "bytes_written_wal": 944810446848,
  "bytes_written_sst": 97598488576,
  "bytes_written_slow": 0,
  "max_bytes_wal": 2663278182,
  "max_bytes_db": 18346403430,
  "max_bytes_slow": 0,
  "read_random_count": 13849705,
  "read_random_bytes": 101520069607,
  "read_random_disk_count": 4571471,
  "read_random_disk_bytes": 64385801679,
  "read_random_buffer_count": 9470115,
  "read_random_buffer_bytes": 37134267928,
  "read_count": 11803227,
  "read_bytes": 269378304838,
  "read_prefetch_count": 11803173,
  "read_prefetch_bytes": 269378089728,
  "read_zeros_candidate": 0,
  "read_zeros_errors": 0
}