SAS is very different from SCSI so all bets are off when comparing the two.  An 
x4 4 lane SAS adapter will support 4 SAS drives.  You will need an interposer 
plugged into the SAS card which splits the four lanes onto four cables.  Then 
plug each drives cable into the interposer and you are completely fanned out.  
One lane per drive (each lane is 3Gb/sec transfer rate, well fast enough for 
one LTO4 tape drive).

Kelly Lipp
CTO
STORServer, Inc.
485-B Elkton Drive
Colorado Springs, CO 80907
719-266-8777
www.storserver.com


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Mark Stapleton
Sent: Thursday, November 20, 2008 10:53 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] IBM 3200 Tape Library SAS adapters

No docs, but you want as many ports as possible for maximum throughput.
Officially, you can put three drives per HBA port (through a switch, not
Y cables). I tell customers that a maximum of two drives per HBA port
will make them a LOT happier; three LTO4 drives could saturate the
connection, and that's a bad thing with tape.

--
Mark Stapleton (mark.stapleton AT cdw DOT com)
CDW Berbee
System engineer
7145 Boone Avenue North, Suite 140
Brooklyn Park MN 55428-1511
763-592-5963
www.berbee.com


> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf
> Of Larry Peifer
> Sent: Thursday, November 20, 2008 12:49 PM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: [ADSM-L] IBM 3200 Tape Library SAS adapters
>
> We are in the process of purchasing an IBM 3200 Tape Library with 4 -
> LTO4
> half-height SAS drives.  Our IBM sales rep and tech support rep are
> telling
> us that we need 4 - 5912 HBAs, one for each drive, to support this
> configuration in our IBM 9117-MMA (p570) host.
>
> From our review of the tech specs it looks like the 5912 Adapter
(PCI-X
> DDR
> Dual -x4 SAS Adapter) should be able to support all four SAS tape
> drives
> from one card using 2- YO cables in the same way it can support 4 disk
> drives.  Can anyone point us to someone or some docs that can give us
> more
> information.
>
> Larry Peifer
> San Onofre Nuclear Generating Station
> AIX System Admin
> TSM system Admin