Welcome to z3
z3 is a ZFS to S3 backup tool. This is basically plumbing around
zfs send and
so you should have at least a basic understanding of what those commands do.
z3 was developed by the awesome engineering team at Presslabs, a Managed WordPress Hosting provider.
For more open-source projects, check Presslabs Code.
z3 status will show you the current state, what snapshots you have on S3 and on the local
z3 backup perform full or incremental backups of your dataset.
z3 restore restores your dataset to a certain snapshot.
zfs SUBCOMMAND --help for more info.
pip install z3
z3 is tested on python 2.7 with latest boto 2 and boto 2.2.2 (python-boto version on Ubuntu 12.04).
# Install pv to get some progress indication while uploading. apt-get install pv # Install pigz to provide the pigz compressors. apt-get install pigz
Most options can be configured as command line flags, environment variables or in a config file,
in that order of precedence.
The config file is read from
/etc/z3_backup/z3.conf if it exists, some defaults are provided by the tool.
S3_SECRET can't be provided on the command line.
For a list of all options see
You'll usually want z3 to only backup certain snapshots (hourly/daily/weekly).
To do that you can specify a
SNAPSHOT_PREFIX (defaults to
COMPRESSOR can be set per filesystem like so:
[fs:tank/spam] SNAPSHOT_PREFIX=delicious-daily-spam COMPRESSOR=pigz4 [fs:tank/ham] SNAPSHOT_PREFIX=weekly-non-spam
Dataset Size, Concurrency and Memory Usage
Since the data is streamed from
zfs send it gets read in to memory in chunks.
Z3 estimates a good chunk size for you: no smaller than 5MB and large enough
to produce at most 9999 chunks. These are S3 limitation for multipart uploads.
Here are some example chunk sizes for different datasets:
- 50 GiB: 5 MiB
- 500 GIB: 53 MiB
- 1 TiB: 110 MiB
- 2 TiB: 220 MiB
Multiply that by
CONCURRENCY to know how much memory your upload will use.
# show global options z3 --help # show status of backups for default dataset z3 status # show status for other dataset; only snapshots named daily-spam-* z3 --dataset tank/spam --snapshot-prefix daily-spam- status
# show backup options z3 backup --help # perform incremental backup the latest snapshot; use pigz4 compressor z3 backup --compressor pigz4 --dry-run # inspect the commands that would be executed z3 backup --compressor pigz4 # perform full backup of a specific snapshot z3 backup --full --snapshot the-part-after-the-at-sign --dry-run # inspect the commands that would be executed z3 backup --full --snapshot the-part-after-the-at-sign
# see restore options z3 restore --help # restore a dataset to a certain snapshot z3 restore the-part-after-the-at-sign --dry-run # inspect the commands that would be executed z3 restore the-part-after-the-at-sign # force rollback of filesystem (zfs recv -F) z3 restore the-part-after-the-at-sign --force
Other command line tools are provided.
pput reads a stream from standard in and uploads the data to S3.
z3_ssh_sync a convenience tool to allow you to push zfs snapshots to another host.
If you need replication you should checkout zrep. This exists because we've already
got zrep between 2 nodes and needed a way to push backups to a 3rd machine.
z3_get called by
z3 restore to download a backup.
Running the tests
The test suite uses pytest. Some of the tests upload data to S3, so you need to setup the following environment:
export S3_KEY_ID="" export S3_SECRET="" export BUCKET="mytestbucket"
To skip tests that use S3:
py.test --capture=no --tb=native _tests/ -k "not with_s3"
Snapshots are obtained using
zfs send, optionally piped trough a compressor (pigz by default),
and finally piped to
Incremental snapshots are always handled individually, so if you have multiple snapshots to send
since the last time you've performed a backup they get exported as individual snapshots
(multiple calls to
zfs send -i dataset@snapA dataset@snapB).
Your snapshots end up as individual keys in an s3 bucket, with a configurable prefix (
S3 key metadata is used to identify if a snapshot is full (
isfull="true") or incremental.
The parent of an incremental snapshot is identified with the
S3 and ZFS snapshots are matched by name.
The S3 health checks are very rudimentary, basically if a snapshot is incremental check that the parent exists and is healthy. Full backups are always assumed healthy.
If backup/restore encounter unhealthy snapshots they abort execution.
pput is a simple tool with one job, read data from stdin and upload it to S3. It's usually invoked by z3.
Consistency is important, it's better to fail hard when something goes wrong than silently upload inconsistent or partial data. There are few anticipated errors (if a part fails to upload, retry MAX_RETRY times). Any other problem is unanticipated, so just let the tool crash.
TL;DR Fail early, fail hard.