As part of implementing crypto I''ve been looking at the zio transform code a fair bit - I still have problems understanding some of it and using it but that isn''t the topic of this mail. I''ve also read a little about some of the functionality that NTFS has for single image storage and how that is implemented. This has made me wonder if there is value in having a generic ZTL interface. The idea would be for this to be pluggable (without modification of the source) a little like STREAMS in away :-). There would need to be a config somewhere (probably held in the pool) that defines what transform plugins are used and in which order they run for reads and writes (and wither they are sync or async ops). A plugin would be able to add options to zfs(1) (and maybe zpool(1m)). Compression and Crypto could both be done as a plugin this way. Without the plugin installed zfs(1) wouldn''t show any compression or crypto options. If this is just compression and crypto I don''t really see the point in building a framework to implement this. Are there other transforms that might be needed that would make this worth while. Just thought I''d share this. [ One last thing why ZTL ? because it is the last three letters of my car registration plate :-) ] -- Darren J Moffat