BtrFS, ZFS, and More

Butter Filesystem. Hold the toast.

I've started experimenting with BtrFS which aims to provide an "advanced and modern filesystem" (heavily compared to ZFS) on Linux. With my new workstation I've started using BtrFS for my home directories (/home) and my build directories (/mnt/slackbuilds) to gain exposure to the filesystem and compare it to ZFS and EXT4 on LVM (all of my other data, including my root disk is on EXT4 on LVM).

I have used ZFS heavily in the past, and using BtrFS is significantly different as many of the fundamental concepts are different. BtrFS has no concept of "pools" or "volume groups" -- instead there are "volumes." BtrFS has no concept of "datasets" or "logical volumes" -- instead there are "subvolumes".

Here's a comparison between ZFS, BtrFS, and EXT4 on LVM:

Comparison

[1] For lack of a better term -- how well the command line interface integrates with the system as a whole, this might be subjective.

For a more complete, but less focused comparison see Wikipedia's Comparison of Filesystems

The Rosetta Stone

1. Task: Create a pool of storage from disks /dev/A, /dev/B, and /dev/C (striped or linear concat)
   1. Using ZFS:
      1. # zpool create TESTPOOL A B C
   2. Using BtrFS:
      1. # mkfs.btrfs -d raid0 /dev/A /dev/B /dev/C
   3. Using EXT4 on LVM:
      1. # pvcreate /dev/A /dev/B /dev/C
      2. # vgcreate TESTPOOL /dev/A /dev/B /dev/C
2. Task: Make storage from pool available to system
   1. Using ZFS:
      1. # zfs set mountpoint=/data TESTPOOL
   2. Using BtrFS:
      1. # mkdir /data
      2. # mount -t btrfs /dev/A /data
      3. Update /etc/fstab
   3. Using EXT4 on LVM:
      1. # mkdir /data
      2. # lvcreate -L _SizeOfVolume_ -n DATA TESTPOOL
      3. # mkfs -t ext4 /dev/TESTPOOL/DATA
      4. # mount /dev/TESTPOOL/DATA /data
      5. Update /etc/fstab
3. Task: Add an additional disk to the pool
   1. Using ZFS:
      1. # zfs add TESTPOOL D
   2. Using BtrFS:
      1. # btrfs device add /dev/D /data
      2. # btrfs filesystem balance /data
   3. Using EXT4 on LVM:
      1. # pvcreate /dev/D
      2. # vgextend TESTPOOL /dev/D
4. Task: Add additional space to a filesystem
   1. Using ZFS:
      1. No action needed
   2. Using BtrFS:
      1. No action needed
   3. Using EXT4 on LVM:
      1. # lvextend -L _SizeToIncreaseTo_ /dev/TESTPOOL/DATA
      2. # resize2fs /dev/TESTPOOL/DATA
5. Task: Remove a disk from the pool
   1. Using ZFS: N/A
   2. Using BtrFS:
      1. # btrfs device delete /dev/A /data
      2. # btrfs filesystem balance /data
   3. Using EXT4 on LVM:
      1. # pvmove /dev/A
      2. # vgreduce TESTPOOL /dev/A
6. Task: Replace operational disk
   1. Using ZFS:
      1. # zfs replace TESTPOOL A D
   2. Using BtrFS:
      1. # btrfs device add /dev/D /data
      2. # btrfs device delete /dev/A /data
      3. # btrfs filesystem balance /data
   3. Using EXT4 on LVM:
      1. # pvcreate /dev/D
      2. # vgextend TESTPOOl /dev/D
      3. # pvmove TESTPOOL /dev/A /dev/D
      4. # vgreduce TESTPOOL /dev/A
7. Task: Take a snapshot of a filesystem
   1. Using ZFS:
      1. # zfs snapshot TESTPOOL@snapshot1
   2. Using BtrFS:
      1. # btrfs subvolume snapshot /data /data/snapshot1
   3. Using EXT4 on LVM:
      1. # lvcreate -s /dev/TESTPOOL/DATA -L _SizeToAllocate_ -n snapshot1
8. Task: Rollback a snapshot
   1. Using ZFS:
      1. # zfs rollback TESTPOOL@snapshot1
   2. Using BtrFS:
      1. Not sure...
   3. Using EXT4 on LVM:
      1. # lvconvert --merge /dev/TESTPOOL/snapshot1
9. Task: Delete a snapshot
   1. Using ZFS:
      1. # zfs destroy TESTPOOL@snapshot1
   2. Using BtrFS:
      1. # btrfs subvolume delete /data/snapshot1
   3. Using EXT4 on LVM:
      1. # lvremove /dev/TESTPOOL/snapshot1