--> ... one drive on each SCSI card.

Both Ultra2 (FC 6205) and Ultra3 (FC 6203) SCSI adapter are dual channel
so you ought to be able to have at least two drives (one on each bus) per
adapter.

Some math:
IBM Ultrium 2 drive - up to 35 MB/s native
3 fibre drives per 2 Gb FC HBA - 200 / 3 = 66 MB/s   ==> even with 2:1
compression ratio you can be easily bottlenecked
2 drives per Ultra3 SCSI bus (if you have FC 6203) - 160 / 2 = 80 MB/s
(over 20% better)
2 drives per FC HBA - ~100 GB/s   (leaves some room to achieve better
compression, for example on Oracle/SAP databases)

--> But I've already got the SCSI cards installed

Do some more math. What would be "cheaper" - replacement of SCSI with FC
or your server/library decreased productivity?

Zlatko Krastev
IT Consultant






Tom Kauffman <KauffmanT AT NIBCO DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
03.09.2003 18:51
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Configuration question


It's that wonderful time of year -- budget time!

I currently have an IBM 3584 with 10 LTO-1 tape drives and two bays. The
drives are all SCSI attached. The lease will be up around August 31 next
year.

I'm planning on replacing the LTO-1 drives with LTO-2 drives. Right now,
I'm
thinking of doing 6 drives as fiber-attach and 4 as SCSI. First, my TSM
host
really has room for just two (more) fiber adapters (660-6M1 with 3 I/O
drawers, with each adapter on a seperate PCI bus). Second, I have my SAP
DB
server configured so I can manually move TSM to it if my TSM server is
down
for a significant length of time -- and there's no room for more fiber
adapters. But I've already got the SCSI cards installed (and the lease for
these systems has 24 months to go).

Does this make sense? I'd end up with 3 drives on each fiber and one drive
on each SCSI card.

We don't do SAN backups and I don't see SAN backups in the near future
(and
if I did, the maximum drive count would be 5 as our clients are currently
configured).

TIA

Tom Kauffman
NIBCO, Inc
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