Re: Marvell 88e8057, and SATA disk cache flushing?

[Venkatesh Srinivas <me@xxxxxxxxxxxxxxxxxxx>]

On Sat, Oct 22, 2011 at 11:42 AM, james <james@mansionfamily.plus.com> wrote:
> 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?

I believe the msk driver does.

> 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.

HAMMER explicitly flushes drive caches.

Our device-mapper linear target does forward FLUSH commands to backing
devices. I don't know about vinum, unfortunately. At first skim of
vinumstart(), it doesn't, but I only quickly scanned it.

UFS does not ever flush drive caches. Boo.

--vs;