Dataset is being sent as a compressed stream by zfs send regardless of the compression option used

[Scrin]

Not entirely sure whether this is a "less-ideal feature" or an actual bug, but I noticed that send_pipe() (in ZfsDataset.py) appends the --compressed option to zfs send (if it's supported), which causes two notable things:

• As per the manual "Streams sent with -c will not have their data recompressed on the receiver side using -o -compress=value. The data will stay compressed as it was from the sender." which prevents using different compression method on the receiver side, which is relatively common case; use fast lz4 in production and gzip for the backups for trading performance for saved space.
• Since the stream is now already compressed by zfs send, it makes the "wrapping" compressor (defined by the zfs_autobackup's --compress flag) very inefficient since it now has to compress already compressed data rather than the raw, uncompressed source data.

Perhaps the inclusion of the --compressed option in zfs send should be removed, or at least made configurable?

[psy0rz]

Yes indeed this is a problem now that we have --compress. Also i didnt realize sometimes the administrator might want to recompress on the other side.

We could either:

• Disable it automaticly when the user specifies --compress.
• Disable it by default and have an extra option called --zfs-compressed that enables zfs send --compressed.

I'm for the second option since i want to keep automatic setting guessing/magic to the minimum and we should let the administrator decide which function is desired.

Perhaps a warning when both --zfs-compressed and --compress are specified.

Anyone following this, let me know your opinion about this. Justice will be swift :)

[Scrin]

The second option sounds better to me. It would also allow a scenario where compression to be applied only on the receiving side, which can be beneficial in cases where the network link is fast and the source host cpu is slow.

[psy0rz]

fixed in the rc3

[psy0rz]

also updated documentation