What kind of compression is used for VEEAM backups?

@steveneashcraft 

about 2:1

Data Compression and Deduplication - User Guide for Microsoft Hyper-V (veeam.com)

it depends on what settings you have entered in the default job.
default is optimal

Compression is part of the data efficiency techniques used to reduce size, it’s a multi-prong approach.

To improve storage efficiency you have the following:

• Compression: this is customisable and you can set to dedupe friendly should you use a deduplication appliance/Windows Server with deduplication enabled (I don’t see any benefits in doing WS with dedupe but just for completeness)
• Deduplication: Veeam will reuse existing blocks within the chain to avoid backing up data a second time.
• Deleted Blocks & swap file exclusions: Veeam will exclude these blocks from being processed by default to reduce backup size, as these blocks & files aren’t often required.
• Block Size: Veeam offers optimisations for tweaking the block size it fetches as part of changed block tracking (CBT). Larger block sizes are faster to process as there’s less of them to track, but if 1KB of a block has changed but you’re fetching 4MB blocks, you’re backing up nearly 4MB of unchanged data alongside this, so incremental files are larger. This inversely causes more API calls when you’ve got more smaller blocks especially when dealing with object storage with metered API calls this can be undesirable.

Finally you have the block cloning/referencing between different backup chains via ReFS/XFS file system integrations to improve data efficiency further. Hopefully this is a good start!

@steveneashcraft  Good shout here that @coolsport00 calls out the compression engines: zlib and lz4. They are configurable, one thing I’ll add is the defaults are good for most use cases.

You can adjust them - but they are a balance of compute | time | storage efficiency. Many of the destinations that are integrated will pre-define the optimal settings.