Title: Backup software: borg vs restic
Author: Solène
Date: 21 May 2021
Tags: backup openbsd unix
Description:
# Introduction
Backups are important, lot of our life is now related to digital data
and it's important to take care of them because computers are
unreliable, can be stolen and mistakes happen. I really like two
programs which are restic and borg, they have nearly the same features
but it's hard to decide between both, this is an attempt to understand
the differences for my use case.
# Restic
Restic is a backup software written in Go with a "push" workflow, it
supports data deduplication within a repository and multiple systems
using the same repository and also encryption.
Restic can backup to a remote sftp server but also many network
services storage like S3/Minio and even more when using with the
program rclone (which can turn any supported backend into a compatible
restic backend). Restic seems compatible with Windows (I didn't try).
(HTM) restic website
# Borg
Borg is a backup software written in Python with a "push" workflow, it
supports encryption, data deduplication within a repository and
compression. You can backup to a remote server using ssh but the
remote server requires borg to be installed.
It's a very good and reliable backup software. It has a companion app
named "borgmatic" to automate the backup process and snapshots
managements (daily/hourly/monthly ... and integrity checking).
*BSD specific note: borg can honor the "nodump" flag in the filesystem
to skip saving those files.
(HTM) borgbackup website
(HTM) borgmatic website
# Experiment
I've been making a backup of my /home/ partition (minus some
directories that has been excluded in both cases) using borg and
restic. I always performed the restic backup and then the borg backup,
measuring bandwidth for each and execution time for each.
There are five steps: init for the first backup of lot of data, little
changes twice, which is basically opening firefox, browsing a few
pages, closing it, refreshing my emails in claws-mail (this changes a
lot of small files) and use the computer for an hour. There is a
massive change as fourth step, I found a few game installers that I
unzipped, producing lot of small files instead of one big file and
finally, 24h of normal use between the fourth and last step which is a
good representation of a daily backup.
## Data
```
restic borg
Data transmitted (MB)
---------------------
Backup 1 (init) 62860 53730
Backup 2 (little changes) 15 26
Backup 3 (little changes) 168 171
Backup 4 (massive changes) 4820 3910
Backup 5 (typical day of use) 66 44
Local cache size (MB)
---------------------
Backup 1 (init) 161 45
Backup 2 (little changes) 163 45
Backup 3 (little changes) 207 46
Backup 4 (massive changes) 211 47
Backup 5 (typical day of use) 216 47
Backup time (seconds)
---------------------
Backup 1 (init) 2139 2999
Backup 2 (little changes) 38 131
Backup 3 (little changes) 43 114
Backup 4 (massive changes) 201 355
Backup 5 (typical day of use) 50 110
Repository size (GB) 65 56
```
## Analysis
Borg was a lot slower than restic but in my experiment the remote ssh
server is a dual core atom system, borg is using a process on the other
end to manage the data, so maybe that CPU was slowing the backup
process. Nevertheless, in my real use case, borg is effectively slower.
Most of the time, borg was more bandwidth effective than restic: it
saved 15% of bandwidth for the first backup and 18% after some big
changes, but in some cases it used a bit more bandwidth. I have no
explanation for this, I guess it depends how file chunks are
calculated, if a big database file is changing then one may be able to
save only the difference and not the whole file. Borg is also
compressing the data (using lz4 by default), this may explain the
bandwidth saving that doesn't work for binary data.
The local cache (typically in /root/.cache/) was a lot bigger for
restic than for borg, and was increasing slightly at each new backup
while borg cache never changed much.
Finally, the whole repo size holding all the snapshots has a different
size for restic and borg, respectively 65 GB and 56 GB, which makes a
14% difference between each which may due to the compression done by
borg.
# Other backup software
I tested Restic and Borg because they are both good software using the
"push" workflow (local computer sends the data) making full snapshots
of every backup, but there are many other backup solution available.
- duplicity: fully scriptable, works over many remote protocols but
requires a full snapshot and then incremental snapshots to work, when
you need to make a new full snapshot it will take a lot of space which
is not always convenient. Supports GPG encrypted backup stored over
FTP, this is useful for some dedicated server offering 100GB of free
FTP.
- burp: not very well known, the setup uses TLS certificates for
encryption, requires a burp server and a burp client
- rsnapshot: based on rsync, automate the rotation of backups, use hard
links to avoid data duplication for files that didn't change between
two backups, it pulls data from servers from a central backup system.
- backuppc: a perl app that will pull data from servers to its
repository, not really easy to use
- bacula: enterprise grade solution that I never got to work because
it's really complicated but can support many things, even saving on
tapes
# Conclusion
In this benchmark, borg is clearly slower but was the most storage and
bandwidth efficient. On the other hand, restic is easier to deploy
(static binary) and supports a simple sftp server while borg requires
borg installed on both sides.
A biggest difference between restic and borg, is that restic supports
multiples systems backup in the same repository, allowing a massive
data deduplication gain across machines, while a borg repository is for
single system (it could work with multiples systems but they should not
backup at the same time and they would have to rebuild the local cache
every time which is slow).
I'll stick with borg because the backup time isn't a real issue given
it's not dramatically slower than restic and that I really enjoy using
borgmatic to automatically manage the backups.
For doing backups to a remote server over the Internet, the bandwidth
efficiency would be my main concern of all the differences, borg seems
a clear winner here.