The state of SAS

[Staffan Thomén <duck%shangtai.net@localhost>]

Hello list

I've fairly recently started to get into SAS as I got a server that supports 
it, and am still a little confused about how it works, and the support we have 
in NetBSD.

The machine has a SuperMicro-branded LSI MegaRAID 2108 card and it works fine 
with the mfi driver, although I don't seem to have any way of configuring it 
from a running system (bioctl can list the volumes and that's about it) which 
is a bit of a drag.

I also recently got a SAS tape drive, and connected it to the system and 
nothing happened. This might of course be because either a) the raid 
controller card does not support tape drives or b) they have to be configured 
and the card bios does not do it automatically.

My questions then are;

How does SAS really work (in NetBSD); specifically tape drives? Is it 
completely transport agnostic and st(4) will just attach?

Can I scan the scsibus and expect things Just Work like with SCSI?

What about with a non-raid HBA?

The mfii driver seems to support some older LSI SAS controllers (9200-series) 
which is fine, are there any other alternatives for non-raid SAS, because raid 
cards are such a pain?

If anyone would be so kind as to reduce my ignorance in the area, I'd be very 
grateful.

Staffan