Compression and Deduplication on a Datto Device

Scope

This article discusses data compression and deduplication on Datto devices.

Overview

By default, all data pools on Datto devices come with compression turned on. Compression saves space and improves performance. This is because time required to compress and decompress the data is less than then time it takes to read and write uncompressed data to the disk.

Compression type

Datto devices use ZFS LZ4 compression to compress data backed up to the device. LZ4 is a lossless data compression algorithm that is focused on compression and decompression speed. The compression ratio changes depending on the contents of the data itself; different algorithms get varying relative compression rates on different kinds of data.

All ZFS data, including NAS share zvols, inherits the compression settings from the zpool property; compression cannot be changed on a share-by-share basis.

Deduplication

Datto devices do not use ZFS deduplication. Incremental backups, however, effectively deduplicate the base image from every backup, using the inverse chain method. More information on the inverse chain can be found here.

Additional resources