Please retag as "New Feature" issue type, as this issue is about incorporating an upstream OpenZFS feature.
OpenZFS just merged ZSTD and ZSTD-FAST compression support.
It would be nice adding support both to the middleware and the GUI.
If done the same way as GZIP, I would suggest the following levels:
- ZSTD-9 (or 7)
These levels give a nice spread of compressionratio and performance profiles.
See the (my) graphs added to the OpenZFS PR on github: