(sorry if my Message-ID header is missing, I am not subscribed to the mailing list, so I reply using mail-archive) > Try btrfs-show-super <device>. The incompat_flags section enumerates the > flags that are on (at least with a reasonably new btrfs-progs). Thanks a lot for this hint - I totally missed that, since I only looked at manpages and features of the "all-in-one" btrfs tool up to now. Also thanks for the hint to /sys/fs/btrfs, this is even more readable! And thanks a lot for your detailed answer(s) in general! > In general it should be safe to activate flags via btrfstune, but since > they'll generally apply only to newly written data, any benefits on a > mature filesystem will be limited. For that reason as well as to get the > benefit of 16K nodesize which you can't except at creation, I recommend > backing up and recreating the filesystem from a fresh mkfs.btrfs. That would certainly be the best option, however, I have two issues with that: - Any replay of a backup will do a lot of writes on the SSD, reducing lifetime. - I did not yet figure out a working way to get a "complete" backup for a btrfs. btrfs send is too slow for me, and rsync does an incomplete backup, since all FS-special attrs (like the NOCOW attr from 'chattr +C') are not copied, even when xattr copy is on. My last backup replay was from an rsync backup (these I do regularly) and afterwards I did a manual fixing of these special attrs, which is some bit of extra work. Also, the machine is offline during backup replay, while I could still use it during a simple rebalance. The good news is my old FS already has 16K leafsize, it's only missing skinny metadata (and no-holes, apparently that's not default in mkfs.btrfs yet?). This reduces the scope of my question a bit - is it sufficient and worthwhile to "btrfstune -x" and then "btrfs balance start -musage=0 /" to convert all metadata, and thus gain some space? Or are the gains not worth it and I should just wait until the next time I need to replay a backup for other reasons? Cheers and thanks for your reply, Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
