Getting Started

Note

This chapter assumes that your systems meet all required prerequisites and you have abgleich installed. For details see chapter on prerequisites and installation.

Workflow

The fundamental idea is to synchronize portions of two zpools on potentially, but not necessarily, two different physical computers. The first one is called the source, the second one is called the target. A typical workflow has three steps:

  1. snap: Creating snapshots on the source side for datasets/volumes containing changes since last snapshot.

  2. backup: Copying those snapshots currently not present on the target from the source to the target.

  3. cleanup: Removing all but the last n snapshots per dataset/volume on the source side. Optionally also remove all but the last m snapshots from the target side which do not overlap with snapshots on the source side.

Example ZFS deployment

For introductory purposes, two machines are assumed to exist: The sourcebox and the targetbox. abgleich runs on the sourcebox. Each machine has a zpool, conveniently named sourcepool and targetpool. The sourcebox might be a workstation or some kid of a server holding data for e.g. virtual machines. This is where “data is created/changed”. The target might be a hot spare machine or simply a remote backup machine. This is where data is synchronized to.

Let’s further assume that everything within the dataset sourcepool/data and below should be synced with the dataset targetpool/sourcebackup/data and below. data is the “prefix” for the source zpool, sourcebackup/data is the corresponding “prefix” for the target zpool. For abgleich to work, sourcepool/data and targetpool/sourcebackup must exist. targetpool/sourcebackup/data can exist, but it does not have to. The latter can be created by abgleich.

Warning

It is highly recommended to set the mountpoint of targetpool/sourcebackup to none before running abgleich for the first time. This avoids unintended changes to the descendants of targetpool/sourcebackup.

Initial configuration

Before a typical workflow can be performed, abgleich must be configured through a configuration file. The CLI provides a dedicated command-line wizard for creating one, abgleich init filename.yaml, but it can of cause also be written by hand.

For the described example deployment, a minimal configuration file perhaps named config.yaml might look as follows:

Snap

Now its time for the first step of the workflow, creating snapshots on the source side, i.e. for sourcepool/data and below. This is performed by abgleich snap config.yaml.

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By default, abgleich only creates snapshots if datasets/volumes actually contain changes. However, this behaviour can be adjusted.

Backup

After creating snapshots on the source side, snapshots are copied from the source side over to the target side in the second step by invoking abgleich backup config.yaml.

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In this step, sourcepool/data and targetpool/sourcebackup/data are recursively compared to figure out what needs to be copied. Perhaps multiple new snapshots have been created for a certain dataset. Or none at all.

Cleanup

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