Adding a second RAIDZ2 (RAID60), speed question

[stefanb]

Hi there,

when I expand a existing RAIDZ2 (lets call vdev1) with one additional raidz2 (called vdev2), how are the old and how is new workload written to zpool?
I think old workload stays on "old" vdev1 and only new workload is striped over both vdevs, right?
This means, only new workload will have an increased i/o performance?
What will happen when vded1 is full? I expect the workload is stored in vdev2 and i/o performance is decreased, right?

Regards
Stefan

 

[cyberjock]

ZFS preferentially chooses the vdev that is more empty for new writes, but also preferentially chooses the idle vdev as necessary. In short, you just add the vdev and ZFS will "make it all work".