[OmniOS-discuss] zpool fragmentation question

[Dominik Hassler]

Hi there,

on my server at home (OmniOS r16, patched to the latest version) I added a brand new zpool (simple 2 HDD mirror).

zpool list shows a fragmentation of 14% on my main pool. I did a recursive snapshot on a dataset on the main pool. transferred the dataset via replication stream to the new pool (zfs send -R mainpool/dataset at backup | zfs recv -F newpool/dataset).

now zpool list shows a fragmentation of 27% on the *newpool* (no other data have ever been written to that pool).

How can this be? Was my assumption wrong that send/recv acts like defrag on the receiving end?