SATA Port Multipliers in FreeBSD (6.3)

[Christopher Key]

Christopher Key wrote:
> I'm looking to substantially expand the storage on my FreeBSD 6.3 home
> media server.  With regards hardware, the simplest way to attach large
> numbers of drives seem to be to use SATA port multipliers, but I've
> been unable to find any consensus on their level of support in
> FreeBSD.  I'm currently looking at a RocketRAID 2314 and SiI3726 based
> port multipliers.  Has any had any experience with this combination?
>
Just a follow up to let anyone else considering a similar set up that I
now have this combination working on 7.1p3 (I upgraded to take advantage
of zfs, and haven't tested 6.3), although there are a couple of
non-obvious problems:

Firstly, in addition to the documented 'device hptrr', 'device scbus'
and 'device da', a kernel with 'device pass' is also required in order
to be able to see individual disks.

Secondly, the card/driver will only expose disks to FreeBSD if it
recognises them as 'legacy disks', i.e. they contain a MBR. 
Fortunately, zfs leaves the first 8k of each disk untouched, so I
created a 'protective mbr' as per gpt partitioned disks.  It has a
single partition of type 0xed (unused, next to 0xee used for by GPT)
running from lba1 to the last lba on the disk, and with CHS start and
end of 1023/255/63.  This clearly has to be done before connecting the
drives to the controller, but is easily done with, e.g. a USB external
enclosure.

Regards,

Christopher Key