When I send a compressed subvol (i.e., one part of a filesystem mounted with the compress mount option) with btrfs-send, does btrfs-send send it compressed, or does it decompress it first?
Similarly, when I receive the subvol with btrfs-receive, does btrfs-receive re-compress?
Best Answer
btrfs-sendwill performreadsyscalls, which means it will decompress the data indeed. Then data are streamed uncompressed, andbtrfs-receivewill performwritesyscalls, which will compress depending on the targetbtrfssystemcompressmount option.So for instance, you could have an existing
btrfssystem with all kinds of compression used for different files, and write to a new one where all data will bezstd-compressed.