I just set up a freenas zfs raid-z2 with 4 drives sata enterprise drives and doing some performance tests. Right now I'm pushing and pulling linux images into the storage. My notebook has a samsung 840pro ssd with 400MB/s local read write speed. Samba4 is used.
I can write with avg 105 MB/s in an continuous stream. I'm impressed, this is is really fine thinking of a 1Gb/s lan.
However reading is pretty slow and network io is jumping from a few kB to 30MB/s probably in avg. about 10MB/s. Adding a l2arc doesn't help.
Any ideas, why the reading performance is so poor? is this normal?