Enhanced Frame Control Assembly; Control Path Failover, Data Path Failover, And Load Balancing - IBM TS3500 Introduction And Planning Manual

Enhanced frame control assembly

The enhanced frame control assembly is a power structure that combines drive
power, library power, and dual ac line cord capabilities. The assembly includes
only two power supplies, dual ac line cords, and a Medium Changer Assembly
(MCA) unit.
The enhanced frame control assembly comes standard with Models L23 and L53,
and can be ordered as a feature code for Models D23 and D53. For two or more
frames that are properly configured, the assembly is constructed such that failure
or repair of a single, particular part does not cause the entire system to fail or
require scheduled downtime for maintenance. For example, the replacement of any
single, failed power supply can be accomplished without affecting the operation of
the library. The two redundant power supplies are fed directly by independent,
dual ac line cords that support only 220 V ac (110 V ac is not supported). The dual
ac line cords come standard on Models L23, D23, L53, and D53, and do not need
to be ordered as an additional feature code.
If dual ac line cords are not desired, both power supplies can be fed by a single
customer outlet by using feature code 1909 (Single Power Source Bifurcated Cable),
however, feature code 1909 cannot be used if feature code 1950 (Power Distribution
Unit) is installed in the same frame.
The enhanced frame control assembly is compatible with the following model
conversions, which must be performed by an IBM Service Representative:
v Model L22 to L23
v Model D22 to D23
v Model L52 to L53
v Model D52 to D53
v Model L23 to L53
v Model D23 to D53
v Model L53 to L23
v Model D53 to D23
Models L23 and D23 equipped with feature code 4871 (TS7700 Backend Switches
mounting hardware) must also have feature code 1950 (Power Distribution Unit),
which enables dual ac power distribution to the Fibre Channel switches as well as
to the enhanced frame control assembly.

Control path failover, data path failover, and load balancing

This section discusses measures that the TS3500 Tape Library uses to control
library and data path failure, and to balance workload.
Command failures and time-outs are costly. You want your library to run smoothly
and efficiently. To ensure continued processing, libraries that are equipped with
Fibre Channel Ultrium and 3592 tape drives offer path failover and load balancing
capabilities that enable the IBM device driver to resend a command to an alternate
path. The alternate path can include another host bus adapter (HBA), Storage Area
Network (SAN), or library control path drive. The device driver initiates error
recovery and continues the operation on the alternate path without interrupting
the application. Path failover and load balancing are built-in features that are
enabled by using a purchased license key.
51
Chapter 1. Introduction