I've been using OMV2 for a while. My System specs are:
AMD Athlon 5350 @2.05Ghz
2x Seagate ST4000LM016 (2x 4TB, RAID0 with ZFS)
1x Crucial M4 128GB mSATA
OpenMediaVault 2 (Backports Kernel)
The problem is, the transfer speeds TO the NAS are very slow, it doesn't matter which protocol is used. NFS is slightly faster than Samba and FTP, but 20MiB/s are just too slow. When reading from a Samba share I get about 110MiB/s, so almost everything the gigabit network can passthrough. When I write something to the share, I got about 6MiB/s.
I tried already several Samba tuning options. The well known socket options, as well as sendfile, aio read/write behind and some others. Nothing helped.
The strange thing is, sometimes I get high transfer speeds of about 80MiB/s on large files, but if I then copy another large file it's slow again. The speed isn't stable and I have no clue how to improve this. Any advices?
The network speed is stable, tested it with iperf very often, it's always about 940MBit/s. My clients running all with Ubuntu.
This isn't a problem about the speed of the ZFS pool, tested it already with transfering a file from an external hdd directly attached to the NAS. I got consistent speeds of up to 120MiB/s.