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attic-backup

19 Mar 2015

motivation

i do mysql backups using mysqldump and then move this into rdiff-backup, rsnapshot or duplicity.

turns out attic [1] is a much better alternative!

using attic for mysql backups

my script produces a mysqldump every night for all databases and stores it in a single tar.bz2 file each so:

this is an outstanding result and to check if attic didn’t scramble any bits i restored the backup and used ‘diff -r dir1 dir2’ and diff didn’t report any difference.

note: the databases are very idle and there is no change most of the time.

dan’s experiments

some stats for normal backups can be found at [2] so i quote what Dan wrote:

Obnam and Attic are two de-duplicating backup programs that seem to have a very similar design, so I’ve been comparing them. Here are my observations and benchmarks. I would be happy to receive corrections and or additions to this information. The Attic author has also written about this at

Important question:

How resilient are the repositories that Obnam and Attic use?  If a
single sector fails on the hard-drive, how much will be lost?  Do the
programs deal with read errors without crashing?

Testing:

Versions used:  Attic 0.10, Obnam 1.5-1ubuntu1, no encryption.

De-duplication:

For this test I used a single 33MB pdf file.  The initial repos were
33MB for Obnam and 28MB for Attic.  Then I added a single byte to the
start of the file.  The Obnam repo went to 65MB while the Attic repo
stayed at 28MB.  Both took about 1s for the initial backup and 0.5s
for the second backup.

The remaining testing was done with a Maildir folder containing
23000 files.  The total length of these files is 126MB, and they
occupy 177MB on disk according to du -sh, because of partially
filled blocks.  Here MB means 1024*1024 bytes.

Archive size, as measured by du -sh:

After one backup:

Attic:                65MB
Obnam:               190MB
Obnam with deflate:  127MB

After a second backup with no changes:  the same.

Speed:

From local SSD to itself.  Warm cache.  First number is initial
backup, second is a repeat with no changes.  minutes:seconds

cp -a:           0:01
Attic:           0:08  0:01
Obnam:           0:51  0:05
Obnam deflate:   0:53  0:05

From local SSD to remote HD, over a so-so wifi connection:

rsync:           0:24  0:01
Attic ssh:       0:28  0:05
Attic sshfs:     0:51  0:08
Obnam sftp:      8:45  0:21
Obnam sshfs:    25:22  0:22

Note that when using Attic with sshfs, no software has to be installed
on the remote host.

As another data point, I use unison to do bidirectional
synchronization of my home directory with an offsite server.  5GB,
56000 files.  When there are no changes, it runs in 1 second (!), 
and when there are changes, it is also very efficient.  Can either
of these programs get close to that speed in the future?

Dan

summary

after obnam failed in any aspect because of performance issues, attic seems to be what obname promised. i might soon bring attic in as a replacement for my current modules. one thing i don’t like too much though is that it requires to run on the target machine and requires a ssh connection and i a) do not want to run a open ssh server at home nor b) keep an active reverse tunnel open:

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