[Discuss] SAS drives

[feenberg at nber.org (Daniel Feenberg)]

I have been experimenting with a Promise 4650 SAS controller and 2 2.5" 
Seagate SAS drives and as someone who has never used a SAS drive 
before I have been surprised by a couple of things.

1) The connector on the drive is a single connector for power and data
and incompatible with the connectors used by 2.5" SATA drives. The
controller came with  cables that connect power to a Molex connector
and data to the controller. Perhaps this is why power supplies continue 
to have so many molex connectors? The controller end of the cable is the
same as a SATA connector, as the controller can handle SATA drives also.

2) Reviews of various SAS controllers on Newegg speak about "directional 
SAS cables" and "SAS expanders", but I haven't been able to find out 
anything about them.

3) The Promise documentation includes almost nothing you want to know.

4) FreeBSD 7.4 won't boot with drives defined on the Promise controller.

5) Windows 7 will boot, but does not include drivers on disk or online 
(they are on a disk supplied with the controller). This is really 
surprising, considering how long this controller has been available.

6) Reviewers on Newegg of SAS controllers often complain about long
boot times, as though the SAS controller was interfering in some way.

7) Reviewers on Newegg of SAS controllers often complain about small
controller caches, but I wonder if this is important if there is plenty
of main memory.

Mostly, I'd like to figure out how to build a fast file server for large
sequential files, and thought this might be a good approach. So far
not so good.