Package: backy
OverviewBacky is a block-based backup and restore utility for virtual machine images.Backy is intended to be:space-, time-, and network-efficienttrivial to restorereliable.To achieve this, we rely on:space-efficient storages (CoW filesystems, content-hashed chunking)using a snapshot-capable source for our volumes (i.e. Ceph RBD)
that allows easy extraction of changes between snapshots,leverage proven, existing low-level tools,keep the code-base small, simple, and well-tested.We also have a few ground rules for the implementation:VM data is stored self-contained on the filesystem and can be
moved between servers using regular FS tools like copy, rsync, or such.No third party daemons are required to interact with backy: no database
server. The scheduler daemon is only responsible for scheduling and simply
calls regular CLI commands to perform a backup. Backy may interact with
external daemons like Ceph or Consul, depending on the source storage
implementation.OperationsFull restoreCheck which revision to restore:$ backy -b /srv/backy/<vm> statusMaybe set up the Ceph environment - depending on your configuration:$ export CEPH_ARGS="--id $HOSTNAME"Restore the full image through a Pipe:$ backy restore -r <revision> - | rbd import - <pool>/<rootimage>Setting up backyCreate a sufficiently large backup partition using a COW-capable filesystem
like btrfs and mount it under/srv/backy.Create a configuration file at/etc/backy.conf. See man page for details.Start the scheduler with your favourite init system:backy -l /var/log/backy.log scheduler -c /path/to/backy.confThe scheduler runs in the foreground until it is shot by SIGTERM.Set up monitoring usingbacky check.Set up log rotation for/var/log/backy.confand/srv/backy/*/backy.log.The file paths given above match the built-in defaults, but paths are fully
configurable.FeaturesTelnet shellTelnet into localhost port 6023 to get an interactive console. The console can
currently be used to inspect the scheduler’s live status.Self-checkBacky includes a self-checking facility. Invokebacky checkto see if there is
a recent revision present for all configured backup jobs:$ backy check
OK: 9 jobs within SLABoth output and exit code are suited for processing with Nagios-compatible
monitoring systems.Pluggable backup sourcesBacky comes with a number of plug-ins which define block-file like sources:fileextracts data from simple image files living on a regular file
system.ceph-rbdpulls data from RBD images using Ceph features like snapshots.flyingcircusis an extension to theceph-rbdsource which we use
internally on theFlying Circushosting platform. It uses advanced features
like Consul integration.It should be easy to write plug-ins for additional sources.Adaptive verificationBacky always verifies freshly created backups. Verification scale depends on
the source type: file-based sources get fully verified. Ceph-based sources are
verified based on random samples for runtime reasons.Zero-configuration schedulingThe backy scheduler is intended to run continuously. It will spread jobs
according to the configured run intervals over the day. After resuming from an
interruption, it will reschedule missed jobs so that SLAs are still kept if
possible.Backup jobs can be triggered at specific times as well: just invokebacky
backupmanually.PerformanceBacky is designed to use all of the available storage and network bandwidth by
running several instances in parallel. The backing storage must be prepared for
this kind of (mixed) load. Finding optimal settings needs a bit of experimentation
given that hardware and load profiles differ from site to site. The following
section contains a few points to start off.Storage backendIf the backing storage is a RAID array, its stripe size should be aligned with
the filesystem. We have made good experiences with 256k stripes. Also check for
512B/4K block misalignments on HDDs. We’re using it usually with RAID-6 and have
seen reasonable performance with both hardware and software RAID.FilesystemWe generally recommend XFS since it provides a high degree of parallelism and is
able to handle very large directories well.Note that the standardcfqI/O scheduler is not a good pick for
highly parallel bulk I/O on multiple drives. Usedeadlineornoop.KernelSince backy performs a lot of metadata operations, make sure that inodes and
dentries are not evicted from the VFS cache too early. We found that lowering
thevm.vfs_cache_pressuresysctl can make quite a difference in total backup
performance. We’re currently getting good results setting it to10.
You may also want to increasevm.min_free_kbytesto avoid page allocation
errors on 10 GbE network interfaces.DevelopmentBacky has switched to usingpoetryto manage its dependencies. This means
that you can usepoetry installto install dependencies from PyPI.If you don’t havebackyin your PATH when developing, enter the poetry
virtualenv withpoetry shellor if you’re using nix withnix develop.You can build backy withpoetry buildmaking a wheel and a tar archive
in thedistdirectory, or by runningnix build.AuthorsChristian Theune <ct@flyingcircus.io>Christian Kauhaus <kc@flyingcircus.io>Daniel Kraft <daniel.kraft@d9t.de>LicenseGPLv3LinksBitbucket repositoryPyPI pageOnline docsBuild serverChangelogUnreleasedSee the fragment files in thechangelog.ddirectory.2.5.1 (2023-10-12)Fix telnetjobscommand2.5.0 (2023-10-11)Separate pool into fast and slow. According to our statistics 90% of jobs are
faster than 10 minutes and after that they might run for hours. We now run
the configured amount of workers both in a fast and slow pool so that long
jobs may delay other long jobs but fast jobs should be able to squeeze
through quickly.Port to Python 3.10+.Continue deleting snapshots even if some are protected.Improve detection for ‘whole object’ RBD export: we failed to detect this is
Ceph is built with wrong version options and shows itself as ‘Development’
instead of a real version.Do not count running jobs as overdue.Regularly log overdue jobs.Delete Tags from former schedulesAdd forget subcommandAdd compatibility to changedrbd showmappedoutput format in Ceph Nautilus.
Ceph Jewel and Luminous clusters remain supported.Use structlog for loggingStatic typechecking with mypyList all manual tags inbacky checkFix crash for non-numeric Ceph version stringsFix a missing lock on distrustusescrivfor changelog managementRestore default value for missing entries on daemon reloadCrash on invalid config while reloadingremove find subcommand and nbd-serverCompute parent revision at runtimeRemove thelastandlast.revsymlinkDistrust revisions on verification failureQuarantine differences between source and backendFix race condition when reloading while generating a status fileAdd nix flake supportCall configured script on (scheduler triggered) backup completion2.4.3 (2019-04-17)Avoid superfluous work when a source is missing, specifically avoid
unnecessary Ceph/KVM interaction. (#27020)2.4.2 (2019-04-17)Optimize handling offline/deletion pending VMs: don’t just timeout. Take
snapshots and make backups (as long as the image exists). (#22345)Documentation update about performance implications.Clean up build system instrumentation to get our Jenkins going again.2.4.1 (2018-12-06)Optimization: bundle ‘unlink’ calls to improve cache locality of VFS metadataOptimization: load all known chunks at startup to avoid further seeky IO
and large metadata parsing, this also speeds up purges.Reduce OS VFS cache trashing by explicitly indicating data we don’t expect
to read again.2.4 (2018-11-30)Add support for Ceph Jewel’s –whole-object diff export. (#24636)Improve garbage collection of old snapshot requests. (#100024)Switch to a new chunked store format: remove one level of directories
to massively reduce seeky IO.Reorder and improve potentially seeky IOPS in the per-chunk write effort.
Do not create directories lazily.Require Python 3.6.2.3 (2018-05-16)Add major operational support for handling inconsistencies.Operators can mark revisions as ‘distrusted’, either all for a backup, or
individual revisions or time ranges.If the newest revision is distrusted then we always perform a full backup
instead of a differential backup.If there is any revision that is distrusted then every chunk will be written
even if it exists (once during a backup, identical chunks within a backup will
be trusted once written).Implement an explicit verification procedure that will automatically trigger
after a backup and will verify distrusted revisions and either delete them or
mark them as verified.Safety belt: always verify content hashes when reading chunks.Improve status report logging.2.2 (2017-08-28)Introduce a new backend storage mechanism, independent of BTRFS: instead of
using COW, use a directory with content-hashed 4MiB chunks of the file.
Deduplication happens automatically based on the 4MiB chunks.Made the use of fadvise features more opportunistic: don’t fail if they are
not supported by the backend as they are only optimizations anyway.Introduce an exponential backoff after a failed backup: instead of retrying
quickly and thus hogging the queue (in the case that timeouts are involved)
we now backoff exponentially starting with 2 minutes, then 4, then 8, …
until we reach 6 hours as the biggest backoff time.You can still trigger an explicit run using the telnet “run” command for
the affected backup. This will put the backup in the run queue immediately
but will not reset the error counter or backoff interval in case it
fails again.Performance improvement on restore: don’t read the restore target. We don’t
have to optimize CoW in this case. (#28268)2.1.5 (2016-07-01)Bugfix release: fix data corruption bug in the new full-always mode. (FC
#21963)2.1.4 (2016-06-20)Add “full-always” flag to Ceph and Flyingcircus sources. (FC #21960)Rewrite full backup code to make use of shallow copies to conserve disk space.
(FC #21960)2.1.3 (2016-06-09)Fix new timeout to be 5 minutes by default, not 5 days.Do not sort blocks any longer: we do not win much from seeking
over volumes with random blocks anyway and this helps for a more
even distribution with the new timeout over multiple runs.2.1.2 (2016-06-09)Fix backup of images containing holes (#33).Introduce a (short) timeout for partial image verification. Especially
very large images and images that are backed up frequently do not profit
from running for hours to verify them, blocking further backups.
(FC #21879)2.1.1 (2016-01-15)Fix logging bugs.Shut down daemon loop cleanly on signal reception.2.1 (2016-01-08)Add optional regex filter to thejobscommand in the telnet shell.Provide list of failed jobs in check output, not only the total number.Addstatus-interval,telnet-addrs, andtelnet-portconfiguration
options.Automatically recover from missing/damaged last or last.rev symlinks (#19532).Use{BASE_DIR}/.lockas daemon lock file instead of the status file.Usability improvements: count jobs, more informative log output.Support restoring to block special files like LVM volumes (#31).2.0 (2015-11-06)backy now accepts a-loption to specify a log file. If no such option is
given, it logs to stdout.Addbacky find -r REVISIONsubcommand to query image paths from shell scripts.Fix monitoring bug where partially written images made the check go green
(#30).Greatly improve error handling and detection of failed jobs.Performance improvement: turn off line buffering in bulk file operations
(#20).The scheduler reports child failures (exit status > 0) now in the main log.Fix fallocate() behaviour on 32 bit systems.Theflyingcircussource type now requires 3 arguments: vm, pool, image.2.0b3 (2015-10-02)Improve telnet console.Provide Nix build script.Generaterequirements.txtautomatically from buildout’sversions.cfg.2.0b2 (2015-09-15)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.2.0b1 (2014-07-07)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).