IBM Tape Solutions for Storage Area Networks and FICON

Chapter 3. SAN building blocks 33

The SAN Data Gateway Router is available as a rack-mounted unit or as a stand-alone

table-top unit. The low-cost router provides one shortwave Fibre Channel port and two

UltraSCSI Differential or UltraSCSI Single-End ports for tape storage attachment.

3.2 IBM SAN Data Gateway

The IBM SAN Data Gateway (2108-G07) was one of the first components of the IBM SAN

solution that allows an easy migration to the SAN environment using Fibre Channel

technology. The SAN Data Gateway connects SCSI and UltraSCSI storage devices to Fibre

Channel environments. It attaches new or existing SCSI storage products to the SAN using

an industry standard Fibre Channel Arbitrated Loop (FC-AL) interface.

The SAN Data Gateway solves three immediate problems:

򐂰 The 25 m cable length restriction for SCSI: The cable can extend up to 500 m

򐂰 Increased bandwidth demand that UltraSCSI storage products can place on the SCSI bus

򐂰 The address limitations of SCSI

The use of hubs in SAN configurations increases the device connectivity, but hubs have

some impact with respect to multiple hosts on the FC-AL loop. These include loop

initialization process and arbitration. If a system is turned off and then turned on, or rebooted,

it may impact the operation of other systems in the FC-AL loop. Many integrators do not

support multi-host loop at all.

The use of switches or directors increases the host

fan-out or number of host connections of

SAN configurations.

The SAN Data Gateway uses Fibre Channel and UltraSCSI channel bandwidth for

high-performance attachment of the following devices:

򐂰 IBM TotalStorage Enterprise Storage Server

򐂰 IBM Magstar 3590 Tape Subsystem in stand-alone, Magstar 3494 Tape Library, and

Magstar 3590 Silo Compatible Tape Subsystem environments

򐂰 IBM Magstar MP 3570 Tape Subsystem or Magstar MP 3575 Tape Library Dataserver

򐂰 IBM 3502 DLT Tape Library

򐂰 IBM Ultrium 358X Tape Subsystems with Linear Tape-Open (LTO) Tape Drives

For the latest list of supported servers, adapters, disk, and tape subsystems on the SAN Data

Gateway, see:

http://www-1.ibm.com/servers/storage/support/san/

Sharing the Gateway between disk and tape products is currently not supported or practical,

because:

򐂰 The IBM TotalStorage Enterprise Storage Server needs all the SCSI attachments.

򐂰 The levels of the HBA driver required for disk and for tape are different. This makes it

impossible to use Gateway-attached disks and tapes on the same host. This will

eventually be fixed, but provides a good illustration of an interoperability problem.

You can use the Gateway either as a stand-alone table top unit or mounted in a standard

19-inch rack. The rack can be either the IBM 2101 Seascape® Solutions rack or an industry

standard rack.