Filesystems

ZFS Deduplication and Compression
Q: Is deduplication of ZFS negativly affected by putting compressed files on it?
A: Yes. Tested by putting similar files (files that well dedup) on a volume in compressed format (RAR5) and completely uncompressed the files from the archives. Maybe different on other compression algorithms? 
Data:
compressed
raw (vm)
136 GB
vol (hypervisor)
136 GB (no compression as data already compressed)
zvol (hypervisor)
103,4 GB (light deduplication)
uncompressed
raw (vm)
297 GB
vol (hypervisor)
248 GB (hv compression)
zvol (hypervisor)
59,7 GB (massive deduplication)