Backup and restore for block devices.
This is work in progress. Parts of this file are currently fiction.
Backy is a block-based backup utility for virtual machines (i.e. volume files).
Backy is intended to be:
- space-, time-, and network-efficient
- trivial to restore
To achieve this, we rely on:
- using a copy-on-write filesystem (like ZFS or btrfs) as the target filesystem to achieve space-efficiency
- using a snapshot-capable main storage for our volumes (e.g. Ceph, LVM, …) that allows easy extraction of changes between snapshots
- leverage proven, existing low-level tools
- keep the code-base small, simple, and well-tested.
backy [-b <backupdir>] init
backy [-b <backupdir>] backup
backy [-b <backupdir>] status
Disaster recovery / full restore
The most important question is: I screwed up - how do I get my data back?
Here’s the fast answer to make a full restore of the most recent backup:
$ cd /srv/backy/my-virtual-machine $ dd if=latest of=/srv/kvm/my-virtual-machine bs=4048000
If you like to pick a specific version, it’s only a little more effort:
$ cd /srv/backy/my-virtual-machine $ backy status == Revisions 2014-04-25 10:07:51 96d8b001-0ffc-4149-8c35-cf003f5638d6 20.00 GiB 252s 2014-04-25 10:13:20 d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec 24.34 MiB 13s == Summary 2 revisions 20.02 GiB data (estimated) $ dd if=96d8b001-0ffc-4149-8c35-cf003f5638d6 of=/srv/kvm/my-virtual-machine bs=4048000
Restoring individual files
The image files are exact copies of the data from the virtual disks. You can use regular Linux tools to interact with them:
$ cd /srv/backy/my-virtual-machine $ ls -lah latest lrwxrwxrwx 1 root root 36 Apr 25 10:13 last -> d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec $ kpartx -av d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec add map loop0p1 (253:9): 0 41934815 linear /dev/loop0 8192 $ mkdir /root/restore $ mount -o ro /dev/mapper/loop0p1 /root/restore $ cd /root/restore $ ls bin boot dev etc home lib lost+found media mnt opt proc root run sbin srv sys tmp usr var
To clean up:
$ cd /srv/backy/my-virtual-machine $ umount /root/restore $ kpartx -av d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec
Do a backup.
This includes checking whether a backup is needed, cleaning up from previous incomplete backups, and removing backups that are no longer needed according to the schedule.
If no backup is needed, just exit silently.
Show backup inventory and provide summary information about backup health.
If a command expects a single revision, you can specify full UUIDs, or numbers. Numbers specify the N-th newest revision (0 being the the newest, 1 the previous revision, and so on).
If multiple revisions may be given you can pass a single revision (as described above) or the word all to match all existing revisions.
- 0: Command worked properly.
- 1: An error occured.
Backy is intended to be compatible with Python 3.3 and 3.4. It is expected to work properly on Linux and Mac OS X, even though specific backends may not be avaible on some platforms:
$ hg clone https://bitbucket.org/ctheune/backy $ cd backy $ virtualenv --python=python3.4 . $ bin/pip install zc.buildout $ bin/buildout $ bin/py.test
Introduce scheduler and rework the main backup command. The backy command is now only responsible for dealing with individual backups.
It does no longer care about scheduling.
A new daemon and a central configuration file is responsible for that now. However, it simply calls out to the existing backy command so we can still manually interact with the system even if we do not use the daemon.
Add consul integration for backing up Flying Circus root disk images with clean snapshots (by asking fc.qemu to use fs-freeze before preparing a Ceph snapshot).
Switch to shorter UUIDs. Existing files with old UUIDs are compatible.
Turn the configuration format into YAML. Old files are still compatible. New configs will be generated as YAML.
Performance: defrag all new files automatically to avoid btrfs degrading extent performance. It appears this doesn’t completely duplicate all CoW data. Will have to monitor this in the future.
- Clean up docs.
- Add classifiers in setup.py.
- More or less complete rewrite expecting a copy-on-write filesystem as the target.
- Flexible backup scheduling using free-form tags.
- Compatible with Python 3.2-3.4.
- Initial open source import as provided by Daniel Kraft (D9T).
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