Anthony's got it right. The RocksDB LZ4 compression will be incremental as new compactions takes place. You can manually issue a full compaction to trigger it if you'd like. If you want to switch back, just remove the compression flag and restart the OSD. New SST files will then be written out uncompressed. Mark On 8/9/25 5:35 PM, Anthony D'Atri wrote:
I *think* this will happen over time as each OSD’s RocksDB compacts, which might be incremental.
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.
I believe so.
Still the question remains on how to bring all existing data over to be compressed. I think the only way is to rewrite the data. There are scripts out there to do this for CephFS, where the same process should work as can be used when migrating existing data to a new data pool. For RBD and RGW, re-write from a client. With RBD you might do something like
rbd export myimage | rbd import - myimage.new; rbd rm myimage ; rbd rename myimage.new myimage
dance, with caution regarding space, names, watchers, client attachments, phase of moon, etc.
With RGW maybe something like rclone or Chorus to copy into a new bucket, rm the old bucket.
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