Problems adding Intel 750 to zfs pool

[dylan at techtangents.com]

Hi,

I've installed an Intel 750 400GB NVMe PCIe SSD in a Dell R320 running 
FreeBSD 10.2-beta-1... not STABLE, but not far behind, I think. 
Apologies if this is the wrong mailing list, or if this has been fixed 
in STABLE since the beta.

Anyway, I've gparted it into 2 partitions - 16GB for slog/zil and 357GB 
for l2arc. Adding the slog partition to the pool takes about 2 minutes - 
machine seems hung during that time. Ping works, but I can't open 
another ssh session.

Adding the l2arc doesn't seem to complete - it's been going 10 minutes 
now and nothing. Ping works, but I can't log in to the local console or 
another ssh session.

I'm adding the partitions using their gpt names. i.e.
zpool add zroot log gpt/slog
zpool add zroot cache gpt/l2arc

The system BIOS is up-to-date. The OS was a fresh 10.1 install, then 
freebsd-update to 10.2-beta2. 10.1 exhibited the same symptoms.

Root is on zfs.

Device was tested to be working on Windows 8.1 on a Dell T1700 workstation.

Any ideas?

Cheers,

Dylan Just