Simple script for replication of single datasets over SSH with zfs send/receive

zfs-replicate.sh

#!/bin/bash

# Source pool or dataset
SOURCE=Storage

# Target location on remote machine
# Note: Ensure all datasets in there are not mounted, otherwise the user on the remote machine needs to have unmount permissions.
TARGET=Storage/Backups/Some-Server

# Datasets to be backed up (relative to source)
DATASETS=(Data)

# Command for ssh connection to remote machine
SSH_COMMAND="ssh -i /some/directory/id_rsa BackupUser@backup.host.example.com"

# Error handling
failure()
{
    echo "An error occured. Exiting."
    trap : 0
    exit 1
}
trap 'failure' 0
set -e

# Backup datasets
for dataset in "${DATASETS[@]}"
do
    source_dataset="$SOURCE/$dataset"
    target_dataset="$TARGET/$dataset"

    # Analyze source dataset
    first_source_snap=$(zfs list -t snapshot -o name -s creation -r "$source_dataset" | grep "^$source_dataset@" | head -1 | cut -d '@' -f2 ; exit "${PIPESTATUS[0]}")
    last_source_snap=$(zfs list -t snapshot -o name -s creation -r "$source_dataset" | grep "^$source_dataset@" | tail -1 | cut -d '@' -f2 ; exit "${PIPESTATUS[0]}")

    # Backups are not possible when no snapshots exist
    if [[ -z "$first_source_snap" || -z "$last_source_snap" ]]
    then
        echo "No snapshots in source '$source_dataset'. Consider setting up zfs-auto-snapshot."
        failure
    fi

    # Analyze remote dataset
    first_target_snap=$($SSH_COMMAND zfs list -t snapshot -o name -s creation -r "$target_dataset" | grep "^$target_dataset@" | head -1 | cut -d '@' -f2 ; exit "${PIPESTATUS[0]}")
    last_target_snap=$($SSH_COMMAND zfs list -t snapshot -o name -s creation -r "$target_dataset" | grep "^$target_dataset@" | tail -1 | cut -d '@' -f2 ; exit "${PIPESTATUS[0]}")

    echo "### Backing up: $source_dataset ($first_source_snap - $last_source_snap) ===> $target_dataset (${first_target_snap:-none} - ${last_target_snap:-none})";

    # It's backup time!
    if [[ -z "$last_target_snap" ]]
    then
        # Send first snapshot to initialize the target
        echo "### Target dataset has no snapshots. Sending initial snapshot before starting incremental backups..."
        zfs send -v "$source_dataset@$first_source_snap" | gzip --fast | mbuffer -s 128k -m 500M -q | $SSH_COMMAND "gzcat | zfs recv -F $target_dataset"
    fi
    zfs send -vI "${last_target_snap:-$first_source_snap}" "$source_dataset@$last_source_snap" | gzip --fast | mbuffer -s 128k -m 500M -q | $SSH_COMMAND "gzcat | zfs recv -F $target_dataset"

    echo "### Done: $source_dataset";
done

trap : 0
echo "Done."