SUMMARY: DLT7000 drives on FC/AL...

Date: Fri Jun 09 2000 - 13:59:14 CDT


Had a number of good responses to this, both on the sun-managers list
and on the Veritas Netbackup list ...

BTW, my use of the term 'FC/AL' in my request caused a number of people to
suggest switched fabric instead - this is indeed the direction we are

Thanks to:

David Chapa
Rob Worman
Peter Buschman
Greg Musi
Bob Lawrence
Nelson Caparrosso
Ayaz Mudarris

Following is one great response I received, which goes into a fair bit
of detail. The general consensus seems to be anywhere between about 5 and 8
drives per switched fabric HBA. One person is running 12 DLT7000s on a single
HBA and is quite happy!

> From: "Peter L. Buschman" <>
> Hi Ross,
> Why are you using FCAL?
> I have an E450 that is presently driving 12 DLT7000s over a single
> FibreChannel switched fabric connection.
> The configuration is as follows:
> 3 Crossroads 4200 SCSI->FibreChannel routers (2 drives per SCSI bus.)
> 1 Brocade Silkworm 2400
> 1 JNI FCI-1063 FibreChannel card.
> At 20MB/s per SCSI bus on the crossroads, the Crossroads will only
> ever push 40MB/s onto the Brocade fabric. Combined, the 3 Crossroads
> routers can push a total of 120MB/s onto the fabric, which could
> potentially overwhelm my single connection from the E450. *However*
> that would mean pushing all 12 DLT700s simultaneously at 10MB/s which
> is highly unlikely since that would require a 2/1 compression ratio
> constantly. In practice, the load is distributed well, and fibrechannel
> has the significant advantage of being full duplex so I can push 100MB/s
> writes and 100MB/s reads through a single HBA.
> If staying within theoretical limits is your concern, then one fibrechannel
> fabric connection is good for 10 DLT7000s and 2 would be good for 20 DLT700s.
> This applies to a full switched fabric and not an arbitrated loop. The fabric
> allows full 100MB/s bandwidth to each port while the loop is 100MB/s shared
> among
> all the loop devices.
> Using conventional wisdom, you should still be able to get 10 DLT7000s on an
> arbitrated loop (maximum.)



Ross Parker            |      UNIX Sys Admin, Perl and C,
Systems/Network Admin  |        Networking and security
Telus Mobility         |
                       |      Lisp has all the visual appeal of oatmeal        |   with fingernail clippings mixed in (Larry Wall)

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