Tag: ZFS

For a few years I have used the Christmas holidays to create a full
backup of my /home on an external hard disk. For that I used a
Bash script around rsync that uses hard links to keep the used disk
space under control. Each backup was saved in a directory named with
the date of the backup. POSIX ACLs were also backed up.

Since last year’s backup I have moved to ZFS (using ZFS on Linux
with Ubuntu 14.04) as filesystem for /home (and others). Since ZFS
makes checksums of data and metadata it has the possibility to
detect corrupted files (and if the data is redundant it can also fix
them). This is a feature I’d like to have for my backups as
well: I’d rather know it when corruption occurs than live in
ignorance.

So the plan is to move the old backups from the external disk to the
ZFS pool in my server. and instead of using hard links I’ll transfer
the backups in order from old to new to the ZFS pool making a
snapshot for each. Additionally I will also turn on compression
(using the lz4 algorithm). Once that is done I will reformat the
external drive and create a ZFS pool called “JaarlijkseBackupPool” on
it (jaarlijks means annual in Dutch).

The old situation

In the current/old situation, this is how much disk space is used
on the external disk (with and without taking the hard links into
account):

$ sudo du -csh /mnt/JaarlijkseBackups/*
102G    /mnt/JaarlijkseBackups/2010-11-28
121G    /mnt/JaarlijkseBackups/2013-02-04
101G    /mnt/JaarlijkseBackups/2013-12-23
324G    total
$ sudo du -clsh /mnt/JaarlijkseBackups/*
102G    /mnt/JaarlijkseBackups/2010-11-28
193G    /mnt/JaarlijkseBackups/2013-02-04
255G    /mnt/JaarlijkseBackups/2013-12-23
549G    total

Copying the data from the Ext4 disk to a temporary ZFS filesystem on my server

The ZFS pool in my server is called storage. In order to save the
POSIX ACLs of the Ext4 system, they need to be enabled when
creating the ZFS filesystem as well. Setting xattr=sa means the
ACLS are stored more efficiently (although this option is not
compatible with other ZFS implementations at this time, so if I
would try to import the ZFS pool in FreeBSD for example, that
information would be inaccessible).

$ zfs create storage/JaarlijkseBackupsOrganized \
      -o compression=lz4 \
      -o acltype=posixacl \
      -o xattr=sa
$ sudo rsync -ahPAXHS --numeric-ids \
     /storage/JaarlijkseBackups/2010-11-28/ \
     /storage/JaarlijkseBackupsOrganized
$ zfs snapshot storage/JaarlijkseBackupsOrganized@2010-11-28

Followed by the same for the same rsync and zfs snapshot
commands for the other two dates.
Once that is finished, this is the status of that ZFS FS:

$ zfs list -r -t all storage/JaarlijkseBackupsOrganized
NAME                                            USED  AVAIL  REFER  MOUNTPOINT
storage/JaarlijkseBackupsOrganized              275G   438G   272G  /storage/JaarlijkseBackupsOrganized
storage/JaarlijkseBackupsOrganized@2010-11-28  1,03G      -  88,9G  -
storage/JaarlijkseBackupsOrganized@2013-02-04  2,33G      -   196G  -
storage/JaarlijkseBackupsOrganized@2013-12-23      0      -   272G  -
$ zfs get -r -t all compressratio storage/JaarlijkseBackupsOrganized
NAME                                           PROPERTY       VALUE  SOURCE
storage/JaarlijkseBackupsOrganized             compressratio  1.13x  -
storage/JaarlijkseBackupsOrganized@2010-11-28  compressratio  1.19x  -
storage/JaarlijkseBackupsOrganized@2013-02-04  compressratio  1.14x  -
storage/JaarlijkseBackupsOrganized@2013-12-23  compressratio  1.12x  -

Partitioning the external disk

The external disk is as 1TB Samsung SATA 3Gbps SpinPoint F2 EcoGreen disk
(type HD103SI, serial number: S1VSJD6ZB02657). The disk uses 512B
sectors:

sudo hdparm -I /dev/sdf |grep Sector
     Logical/Physical Sector size:           512 bytes

Before using it with ZFS, it needs to be partitioned. I used
parted:

$ parted /dev/sdf
GNU Parted 2.3
Using /dev/sdf
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Model: ATA SAMSUNG HD103SI (scsi)
Disk /dev/sdf: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  1000GB  1000GB  primary  ext4

(parted) mklabel
New disk label type? gpt
(parted) u
Unit?  [compact]? MB
(parted) p
Model: ATA SAMSUNG HD103SI (scsi)
Disk /dev/sdf: 1000205MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start  End  Size  File system  Name  Flags

(parted) mkpart
Partition name?  []? JaarlijkseBackups-HD103SI-S1VSJD6ZB02657
File system type?  [ext2]? zfs
Start? 1M
End? 1000204M
(parted) p
Model: ATA SAMSUNG HD103SI (scsi)
Disk /dev/sdf: 1000205MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End        Size       File system  Name                                  Flags
 1      1,05MB  1000204MB  1000203MB  ext4         JaarlijkseBackups-HD103SI-S1VSJD6ZB0

(parted) q

This removes the old partition table and creates a new GPT
partition table (which allows naming partitions). Next I set the
units to MB so I can leave 1MB at the beginning and end of the
partition (can be helpful when importing this pool in
e.g. FreeBSD). The disk also shows up in /dev/disk/by=partlabel
now.

Creating the new ZFS pool

$ zpool create -o ashift=9 JaarlijkseBackupPool \
    /dev/disk/by-partlabel/JaarlijkseBackups-HD103SI-S1VSJD6ZB0
$ zpool status JaarlijkseBackupPool
  pool: JaarlijkseBackupPool
 state: ONLINE
  scan: none requested
config:

        NAME                                    STATE     READ WRITE CKSUM
        JaarlijkseBackupPool                    ONLINE       0     0     0
          JaarlijkseBackups-HD103SI-S1VSJD6ZB0  ONLINE       0     0     0

errors: No known data errors

Migrating the data

Now that the new ZFS pool and filesystem are all in place, it is
time to move the backups to the new place, starting with the oldest
backup. The -R option also make sure the attributes like
compression and xattr are transferred to the new FS. The
following commands send each snapshot to the new pool (the -n
option of zfs receive is for doing a dry run, just to show how it
works). After the first snapshot is sent, the other two are sent
using the -i option to zfs send so that only the incremental
differences between the snapshots are sent.

$ zfs send -vR storage/JaarlijkseBackupsOrganized@2010-11-28 | \
      zfs receive -Fvu JaarlijkseBackupPool/oldRsyncBackups
$ zfs send -vR -i storage/JaarlijkseBackupsOrganized@2010-11-28 \
    storage/JaarlijkseBackupsOrganized@2013-02-04 | \
    zfs receive -Fvu JaarlijkseBackupPool/oldRsyncBackups
$ zfs send -vR -i storage/JaarlijkseBackupsOrganized@2013-02-04 \
      storage/JaarlijkseBackupsOrganized@2013-12-23 | \
      zfs receive -Fvu JaarlijkseBackupPool/oldRsyncBackups -n
send from @2013-02-04 to storage/JaarlijkseBackupsOrganized@2013-12-23 estimated size is 84,3G
total estimated size is 84,3G
TIME        SENT   SNAPSHOT
would receive incremental stream of storage/JaarlijkseBackupsOrganized@2013-12-23 into JaarlijkseBackupPool@2013-12-23
14:09:16   4,22M   storage/JaarlijkseBackupsOrganized@2013-12-23
14:09:17   8,46M   storage/JaarlijkseBackupsOrganized@2013-12-23
14:09:18   18,4M   storage/JaarlijkseBackupsOrganized@2013-12-23
14:09:19   24,8M   storage/JaarlijkseBackupsOrganized@2013-12-23
^C
$ zfs send -vR -i  storage/JaarlijkseBackupsOrganized@2013-02-04 \
      storage/JaarlijkseBackupsOrganized@2013-12-23 | \
      zfs receive -Fvu JaarlijkseBackupPool/oldRsyncBackups

Add this year’s backup

At first I tried to add the new backups also to the
oldRsyncBackups FS, but that didn’t work (at least not with an
incremental backup), so I ended up making a new backup. The extra
cost in disk space is not a real problem. Disk space is rather
cheap and the current configuration will last me at least one more
year. So after creating a snapshot called 2014-12-26 of my
/home I ran:

   $ zfs send -v  storage/home@2014-12-26 | \
      zfs receive -Fu JaarlijkseBackupPool/home
$ zfs list -r -t all JaarlijkseBackupPool
NAME                                              USED  AVAIL  REFER  MOUNTPOINT
JaarlijkseBackupPool                              581G   332G    30K  /JaarlijkseBackupPool
JaarlijkseBackupPool/home                         311G   332G   311G  /JaarlijkseBackupPool/home
JaarlijkseBackupPool/home@2014-12-26             51,2M      -   311G  -
JaarlijkseBackupPool/oldRsyncBackups              271G   332G   267G  /JaarlijkseBackupPool/oldRsyncBackups
JaarlijkseBackupPool/oldRsyncBackups@2010-11-28   974M      -  87,1G  -
JaarlijkseBackupPool/oldRsyncBackups@2013-02-04  2,23G      -   193G  -
JaarlijkseBackupPool/oldRsyncBackups@2013-12-23      0      -   267G  -
$ zfs get -r compressratio JaarlijkseBackupPool
NAME                                             PROPERTY       VALUE  SOURCE
JaarlijkseBackupPool                             compressratio  1.15x  -
JaarlijkseBackupPool/home                        compressratio  1.17x  -
JaarlijkseBackupPool/home@2014-12-26             compressratio  1.17x  -
JaarlijkseBackupPool/oldRsyncBackups             compressratio  1.13x  -
JaarlijkseBackupPool/oldRsyncBackups@2010-11-28  compressratio  1.19x  -
JaarlijkseBackupPool/oldRsyncBackups@2013-02-04  compressratio  1.14x  -
JaarlijkseBackupPool/oldRsyncBackups@2013-12-23  compressratio  1.12x  -

Finishing up

In order to be able to disconnect the external drive without
damaging the filesystems use

zpool export JaarlijkseBackupPool

Later, the drive/pool can be imported using the zpool import
command.

Now that the migration is done, the intermediate filesystem
(including the snapshots) can also be removed:

zfs destroy -r storage/JaarlijkseBackupsOrganized

For reference: the old rsync script

#!/bin/sh
#
# Time-stamp: <2013-02-04 16:48:31 (root)>
# This scripts helps me create my annual backups to an external hard
# disk. The script uses rsync's hard link option to make hard links to
# the previous backups for files that haven't changed. It makes the
# backup based on an LVM snapshot it creates of the LV that contains
# the /home partition.
# This script needs to be run as root.
 
today=`date +%F`
olddate="2013-02-04"
 
srcdir="/mnt/backupsrc/"
destdir="/mnt/backupdest/JaarlijkseBackups/$today"
prevdir="/mnt/backupdest/JaarlijkseBackups/$olddate"
 
# LVM options
VG=raid5vg
LV=home
 
# rstnc options
options="-ahPAXHS --numeric-ids"
exclusions="--exclude 'lost+found/'"
#  --exclude '*/.thumbnails'"
# exclusions="$exclusions --exclude '*/.gvfs/'"
# exclusions="$exclusions --exclude '*/.cache/' --exclude '**/Cache'"
# exclusions="$exclusions --exclude '*/.recycle/'"
 
# Check to see if the previous backup directory exists
if [ ! -d $prevdir ]; then
    echo "Error: The directory with the previous back up ($prevdir) doesn't exist" 1>&2
    exit 1
fi
 
# Make a snapshot of the home LV that we can backup
lvcreate -L15G -s -n snap$LV /dev/$VG/$LV
mount /dev/$VG/snap$LV $srcdir
 
 
# Start the backup, first a dry-run, then the full one
rsynccommand="rsync $options $exclusions --link-dest=$prevdir $srcdir $destdir"
 
$rsynccommand -n
 
# Wait for user input
echo "This was a dry run. Press a key to continue with the real stuff or"
echo "hit Ctrl-c to abort."
read dummy
 
$rsynccommand

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