Using Direct-Attach Drives - Spectra Logic T-Series Spectra T200 User Manual

To consolidate port usage on a switch, all four drives can be configured for
access through a single port. In a more complex configuration, the QIP can
be configured so that all drives are visible through both ports. Such a
configuration is typically used in a shared storage environment or an
environment with failover capabilities. Note that if drives are visible to
multiple servers, your backup software must support this visibility.
Otherwise server contention for a single drive can create network and
system problems.

Using Direct-Attach Drives

The T200, T380, and T680 libraries also support connecting a Fibre Channel
network or SCSI bus directly to drives that have a native Fibre Channel or
SCSI interface, respectively. Using direct-attach drives provides a cost-
effective way to gain the benefits of an enterprise-class library without
requiring the use of QIPs.
In a direct-attach configuration, one drive in a partition is designated as the
exporting or master drive. The SCSI commands to control the motion of the
transporter within the partition are sent from the host to the master drive's
logical unit number 1 (LUN 1). The master tape drive passes the robotic
control commands to the transporter. SCSI commands to control the
operation of the master drive are sent from the host to LUN 0 of the drive.
With a direct-attach configuration, drives are added to a partition by
connecting them to the master drive using a Fibre Channel arbitrated loop
or by daisy-chaining them on a SCSI bus. Keep in mind that all of the Fibre
Channel drives on an arbitrated loop or SCSI bus must share the data
transfer capacity (bandwidth) of the interface. Having multiple devices on
the same loop or bus can negatively impact the performance of all the
devices.
Direct Attach Fibre Channel
The LTO-4 Fibre Channel drives used with the library are equipped two
Fibre Channel ports. Although the two ports on an LTO-4 Fibre Channel
drive cannot be used simultaneously, they can be used to provide failover
capability in the event that communication to the port currently in use is
interrupted. This failover can be can be accomplished several ways,
including:
December 2008
Manually disconnect the fiber optic cable from the failed port and
connect it to the other port. You may need to reconfigure your host
software to recognize the alternate port.
Network Connectivity
T200, T380, and T680 Libraries
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