'Timemachine'ish backup with ZFS and rsync

• MacOS X 10.5 with ZFS R/W (ZFS on MacOS-Forge), Linux with ZFS-FUSE, FreeBSD with ZFS or Solaris/OpenSolaris
• rsync
• external backup hard drive (USB, FireWire, …)

My tutorial is for MacOS X, but it can be adapted to any of the Systems that support the ZFS file system

I used the steps from the ZFS on MacOS-Forge site to create a ZFS pool on an external USB drive: Finding the disk:

# diskutil list . . . /dev/disk2 #: type name size identifier 0:
Apple\_partition\_scheme *9.4 GB disk2 1: Apple\_partition\_map 31.5 KB
disk2s1 2: Apple\_HFS FW 9.2 GB disk2s3

writing a GPT label on the external disk (be sure to not format your 'main' disk here!):

# diskutil partitiondisk /dev/disk2 GPTFormat ZFS %noformat% 100%
Started partitioning on disk disk2 Creating partition map 
[ +0%..10%..20%..30%..40%..50%..60%..70%..80%..90%..100% ] 
Finished partitioning on disk disk2 /dev/disk2 
#: type name size identifier 0: GUID\_partition\_scheme *9.4 GB disk2 1: EFI 200.0 MB disk2s1 2: ZFS 9.0 GB disk2s2

creating a ZFS pool on the disk called 'macbook-backup':

# zpool create macbook-backup /dev/disk2s2

enable compression on the new pool and disable ATIME:

# zfs set compression=on macbook-backup 
# zfs set atime=off macbook-backup

the hard drive is now prepared.

now I create the first full backup, which I call the 'base' backup. For this I create a new file system called 'base' in the ZFS pool 'macbook-backup':

# zfs create macbook-backup/base

next I copy all files from my backup-source directory (or the whole source disk) to the backup:

# rsync -avh --progress --delete /Users/myuser /Volumes/macbook-backup/base/

depending on the size of the data to backup, this will take a while.

Once the backup is finished, we can access all files under /Volumes/macbook-backup/base. With the ZFS command I can check the compression-ratio of our backup:

# zfs get all macbook-backup/base NAME PROPERTY VALUE SOURCE
macbook-backup/base type filesystem - 
macbook-backup/base creation Wed Jan 31 9:08 2007 - 
macbook-backup/base used 2.21G - 
macbook-backup/base available 1.76G - 
macbook-backup/base referenced 2.21G - 
macbook-backup/base compressratio 1.38x - 
macbook-backup/base mounted yes - 
macbook-backup/base quota none default 
macbook-backup/base reservation none default 
macbook-backup/base recordsize 128K default 
macbook-backup/base mountpoint /Volumes/macbook-backup/base default 
macbook-backup/base sharenfs off default 
macbook-backup/base shareiscsi off default 
macbook-backup/base checksum on default 
macbook-backup/base compression on local 
macbook-backup/base atime off local 
macbook-backup/base devices on default 
macbook-backup/base exec on default 
macbook-backup/base setuid on default 
macbook-backup/base readonly off default 
macbook-backup/base zoned off default 
macbook-backup/base snapdir hidden default 
macbook-backup/base aclmode groupmask default 
macbook-backup/base aclinherit secure default 
macbook-backup/base canmount on default 
macbook-backup/base xattr on default

Now, a few weeks later, I want to make a new, incremental backup. So I create a new snapshot of the base file system and then clone that snapshot into a new file system:

zfs snapshot macbook-backup/base@20080804 
zfs clone macbook-backup/base@20080804 macbook-backup/20080804

The directory for my new, incremental backup will be /Volumes/macbook-backup/20080804. So far the new file system does not use any space on the hard drive. Now I do the new backup with 'rsync':

# rsync -avh --progress --delete /Users/myuser /Volumes/macbook-backup/20080804/

The new backup will only take as much new space on the backup hard drive as there were changes compared to the base backup. But still I am able to browse through the file system at /Volumes/macbook-backup/20080804 and see all files that were available at the date of the 2nd backup.

Any subsequent snapshots for more backups will be done from the 20080804 file system.