IBM XIV Gen3 Series, Planning Manual

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Three redundant configurations are described: 12 paths to each volume, 6 paths to
each volume, and minimal cabling. Each of these configurations has no single
point of failure:
v If an interface module fails, each host remains connected to all other interface
modules.
v If a Fibre Channel switch fails, each host remains connected to at least three
interface modules.
v If a host bus adapter (HBA) on a host fails, the host remains connected to at
least three interface modules.
v If a host cable fails, the host remains connected to at least three interface
modules.
The following example configurations are for an XIV system over a Fibre Channel
with six interface modules. For an XIV system over a Fibre Channel with three
interface modules, fewer paths are used, but the principle of balancing paths across
all interface module still applies.
The minimum supported configuration is paths to two different interface modules.
One path to a single interface module is not supported.
Host system can have as many HBAs as needed to support the operating system,
application, and overall performance requirements.
In an XIV system, each interface module has four Fibre Channel ports.
For supported interoperability configurations, see the System Storage
Interoperation Center website (www.ibm.com/systems/support/storage/config/
ssic).
Redundant configuration with six paths to each volume
Figure 13 on page 56 illustrates a redundant configuration in which all six interface
modules are accessed by using six paths per LUN on the host. This configuration
is recommended for most general-purpose configurations. Host reliability during
path error recovery on certain operating systems is complicated by increasing the
number of paths per LUN. For host systems with two HBAs, the six paths per
LUN method is recommended.
In this configuration:
v Each host is equipped with dual HBAs. Each HBA (or HBA port) is connected to
one of two Fibre Channel switches.
v Each Fibre Channel switch has a connection to a separate Fibre Channel port on
each of the six interface modules.
v One host uses the first three paths per fabric, and the next host uses the three
other paths per fabric.
v If a fabric fails, all interface modules are still used.
v Each volume has six paths.
Chapter 7. Network and host connectivity requirements
55