Marvell 88e8057, and SATA disk cache flushing?

[james]

I need to replace my old NAS and I have some hardware to use, but plan A 
failed dismally because Illumos does not have a working driver for the 
Marvell 88e8057 GegE chip on my Saphire mobo - an AMD E350 device which 
I have in a small case (otherwise I'd just add another NIC).

So:

1) does dragonfly support this chip?

Also - while I'm attracted to swap cache (and I have an SSD that I would 
have used as boot, L2ARC and ZIL) I'm a little concerned that the 
situation with flushing caches on hard disks isn't as clear as it is 
with ZFS, which I trust to use write back cackes and flush explicitly.

So:

2) Does Dragonfly have proper support for flushing write back caches on 
SATA drives?

I have read the notes on 'fsync flush modes' in hammer(8), but this does 
not discuss whether fsync writes to the drive assuming write-through, or 
forces a drive cache flush.

I'm also interested in whether such flushes will work if I configure the 
4-off 2TB drives as a software RAID5 array.

Thanks
James