On Tue, Dec 16, 2014 at 12:21 PM, Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx> wrote: > Your requests aren't bad at all, but they aren't new. Everyone wants > btrfs because it was hyped as the filesystem of the future. tl;dr Those who want it, want it for the features, and much simpler access to those features. Not because of hype. Raid, resizing, snapshots, are much easier with Btrfs separately let alone in combination. And they're safer because the nomenclature is nowhere near as obscure or varied due to the differing syntax of mdadm, lvm, and mkfs. Today. mkfs.btrfs -draid5 /dev/sd[bcde] vs mdadm -C md0 -n 4 -l raid5 /dev/sd[bcde] mdadm --detail --scan >> /etc/mdadm.conf pvcreate /dev/md/md0 vgcreate VG /dev/md/md0 lvcreate -l 95%FREE -T VG/thinp -V 2500M -n home mkfs.xfs /dev/VG/home mkfs.btrfs doesn't need to sync, so it's a < 2 second mkfs. It's hours or days for conventional raid sync. How about growing by adding a new device? btrfs device add /dev/sdf <mountpoint> vs mdadm --add /dev/md/md0 /dev/sdf mdadm --grow --raid-devices=5 /dev/md/md0 pvresize /dev/md/md0 lvextend -L+100G VG/home xfs_growfs /dev/VG/home The mdadm add/grow requires a reshape. Btrfs doesn't. And there are inefficiencies in resizing XFS or ext4 that don't apply to Btrfs. Today, there's some bug preventing the grow/reshape from completing, so it's not like everyone except Btrfs is immune to showstopper bugs. So right now I can't even complete the above grow for md+lvm+xfs, while the raid5 one not only works but it's faster. https://bugzilla.kernel.org/show_bug.cgi?id=89851 How about I take a snapshot of /home, and then accidentally delete a file and want to rollback? btrfs subvolume snapshot /home /home.1 rm -f /home/chris/importantdonteverdelete.tar.gz cp --reflink /home.1/chris/importantdonteverdelete.tar.gz /home/chris/ This completes instantly regardless of the file's size. vs lvcreate -s --name home_snap VG/home rm -f /home/chris/importantdonteverdelete.tar.gz lvchange -ay -K VG/home_snap mount -o nouuid /dev/VG/home_snap /mnt/homesnap cp /mnt/homesnap/importantdonteverdelete.tar.gz /home/chris/ Not the end of the world, but it's still more lines to remember and type, I had to man lvchange to recall the -K, and this method requires a full file copy which is slower and takes up space in the pool. -- Chris Murphy -- desktop mailing list desktop@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/desktop
