IBM System Storage TS3500, Introduction And Planning Manual

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Multi-Path Architecture
This topic explains Multi-Path Architecture feature of the TS3500 Tape Library,
which allows Open Systems applications to share the library's robotics.
The TS3500 Tape Library features the storage area network (SAN)-ready Multi-Path
Architecture, which allows homogeneous or heterogeneous Open Systems
applications to share the library's robotics without middleware or a dedicated
server (host) acting as a library manager. The SAN-ready Multi-Path Architecture
makes sharing possible by letting you partition the library's storage slots and tape
drives into
logical libraries . Servers can then run separate applications for each
logical library. This partitioning capability extends the potential centralization of
storage that the SAN enables. Partitioning also provides investment protection for
Ultrium 1 and Ultrium 2 tape drives if your application does not support the
mixing of Ultrium 1, Ultrium 2, Ultrium 3, Ultrium 4, Ultrium 5, and Ultrium 6
tape drives and media in the same logical library. The Multi-Path Architecture is
compliant with the following attachment interfaces:
v
Small computer system interface (SCSI)
v
Fibre channel
The Multi-Path Architecture of the TS3500 Tape Library is designed to provide the
capability to share the library robotics. This is accomplished by partitioning the
library into as many as 192 logical libraries (up to the number of drives installed),
and providing each logical library its own separate and distinct drive(s), storage
slots, and control paths. Input/output (I/O) slots are shared on a first come, first
serve basis. This type of partitioning is designed to allow heterogeneous
applications to share the library robotics independent of each other. Cartridges
under library control are not shared between logical libraries, nor are they allowed
to be moved between logical libraries. An example of heterogeneous sharing is a
Microsoft Windows 2003 application using the drive and storage slots of one
logical library, while a UNIX application uses the drive and slots of another logical
library. Logical libraries can also be used for separating Ultrium 2 tape dives and
cartridges from Ultrium 4 tape drives and cartridges, or 3592 tape drives and
cartridges, for applications that do not support mixing the drives in the same
logical library.
Whether partitioned or not, the TS3500 Tape Library is certified for SAN solutions
(such as LAN-free backup).
The Multi-Path Architecture also lets you configure additional control paths for
any one logical library. A
control path is a logical path into the library through
which a server sends standard SCSI Medium Changer commands to control the
logical library. Additional control paths reduce the possibility of failure in one
control path causing the entire library to be unavailable. Use of the control path
failover feature further reduces that possibility.
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IBM System Storage TS3500 Tape Library with ALMS: Introduction and Planning Guide
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