Release notes https://ceph.io/en/news/blog/2024/v19-2-0-squid-released/#highlights say:
BlueStore RocksDB LZ4 compression is now enabled by default to improve average performance and "fast device" space usage.
On one EC pool with many files I have such warnings: osd.6 spilled over 8.0 GiB metadata from 'db' device (36 GiB used of 60 GiB) to slow device and hope that the LZ4 compression might help with that. What do I need to do to "migrate" my OSDs to that? I already upgrade the cluster to Ceph 19. Running grep 'Options.compression: ' /var/log/ceph/ceph-osd.6.log already shows the switch from rocksdb: Options.compression: NoCompression to rocksdb: Options.compression: LZ4 in the logs. But does restarting the OSDs already automtaically compress everything with LZ4, or do I need to run some operation such as ceph daemon osd.6 compact or similar to make sure that existing data is actually compressed? Also, could anybody clarify whether this setting is `compression_algorithm` from https://docs.ceph.com/en/squid/rados/operations/pools/#setting-pool-values https://docs.ceph.com/en/squid/rados/configuration/bluestore-config-ref/#con... or if that's something different (e.g. if that's "actual data" instead of "metadata")? I suspect it's different, because `ceph config show-with-defaults osd.6 | grep compression` reveals: bluestore_compression_algorithm snappy bluestore_compression_mode none bluestore_rocksdb_options compression=kLZ4Compression,... From this it looks like `bluestore_compression*` is the "Inline compression" for data (https://docs.ceph.com/en/reef/rados/configuration/bluestore-config-ref/#inli...), and `bluestore_rocksdb_options` is what the "RocksDB compression" is about. Still the question remains on how to bring all existing data over to be compressed. Thanks!