High Availability Hmc Configuration - IBM Power 720 Overview

Notes: The service processor is used to monitor and manage the system hardware
resources and devices. The two service processor HMC ports run at a speed of 100 Mbps.
Both HMC ports are visible only to the service processor and can be used to attach the
server to an HMC or to access the ASMI options from a client web browser using the
HTTP server integrated into the service processor internal operating system.
When no IP address is set, by default, the configurations are as follows:
– Service processor eth0 or HMC1 port is configured as 169.254.2.147 with netmask
– Service processor eth1 or HMC2 port is configured as 169.254.3.147 with netmask
For more information about the service processor, see "Service processor" on page 174.

2.11.2 High availability HMC configuration

The HMC is an important hardware component. When in operation, Power Systems servers
and their hosted partitions can continue to operate when no HMC is available. However, in
such conditions, certain operations cannot be performed, such as a dynamic LPAR
reconfiguration, a partition migration using PowerVM Live Partition Mobility, or the creation of
a new partition. You might therefore decide to install two HMCs in a redundant configuration
so that one HMC is always operational, even when performing maintenance of the other one,
for example.
If redundant HMC functionality is what you want, a server can be attached to two independent
HMCs to address availability requirements. Both HMCs must have the same level of
Hardware Management Console Licensed Machine Code Version 7 and installed fixes to
manage POWER7+ processor-based servers or an environment with a mixture of POWER5,
POWER5+, POWER6, POWER6+, POWER7, and POWER7+ processor-based servers. The
HMCs provide a locking mechanism so that only one HMC at a time has write access to the
service processor. Both HMCs should be available on a public subnet to allow full
synchronization of functionality. Depending on your environment, you have multiple options to
configure the network.
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IBM Power 720 and 740 Technical Overview and Introduction
255.255.255.0.
255.255.255.0.