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Introduction and overview

The Hardware Management Console (HMC) is a dedicated workstation that allows you to configure and manage partitions. To perform maintenance operations, a graphical user interface (GUI) is provided.

Link to the IBM Hardware Management Console (HMC) Best Practices

Functions performed by the HMC include:

Creating and maintaining a multiple partition environment
Displaying a virtual operating system session terminal for each partition
Displaying a virtual operator panel of contents for each partition
Detecting, reporting, and storing changes in hardware conditions
Powering managed systems on and off
Acting as a service focal point
Activating CoD

Note: POWER4 systems use a serial line to communicate with the HMC. This has changed with POWER5. The POWER5 systems use a LAN connection to communicate with the HMC. POWER4 and POWER5 systems cannot be managed by the same HMC.

Basic HMC considerations

The Hardware Management Console (HMC) is based on the IBM eServer xSeries® hardware architecture running dedicated applications to provide partition management for single or multiple servers called managed systems. There are two types of HMCs depending on the CPU architecture of the managed systems:

HMC for POWER4 systems
HMC for POWER5 systems

A single HMC cannot be used to manage a mixed environment of POWER4 and POWER5 systems.

The HMC 3.x code version is used for POWER4 managed systems and HMC 4.x for POWER5 systems (iSeries and pSeries®). For managing POWER5 pSeries machines, HMC 4.2 code version or later is required.

An HMC is not required if the system runs in full system partition. For a partitioned environment an HMC is required. It is recommended to have two HMCs installed for high availability considerations. Previous HMC models with the latest HMC code level are also supported.

The maximum number of HMCs supported by a single POWER5 managed system is two. The number of LPARs managed by a single HMC has been increased from earlier versions of the HMC to the current supported release as shown in Table 3.

HMC connections

During the installation of the HMC, you have to consider the number of network adapters required. You can have up to three Ethernet adapters installed on an HMC. There are several connections you have to consider when planning the installation of the HMC:

HMC to the FSP (Flexible Service Processor): It is an IP-based network used for management functions of the POWER5 systems; for example, power management and partition management.
Note: It is recommended to configure this connection as a private network.
POWER5 systems have two interfaces (T1 and T2) available for connections to the HMC. It is recommended to use both of them for redundant configuration, and high availability. Depending on your environment, you have multiple options to configure the network between the HMC and FSP. The default mechanism for allocation of the IP addresses for the FSP ports is dynamic. The HMC can be configured as a DHCP server which allocates the IP address at the time the managed system is powered on. Static IP address allocation is also an option. You can configure the FSP ports with a static IP address by using the Advanced System Management Interface (ASMI) menus. However not all POWER5 servers support this mechanism of allocation. Currently p575, p590, and p595 servers support only DHCP.
Note: Either eth0 or eth1 can be a DHCP server on the HMC.
HMC to partitions: HMC requires TCP/IP connection to communicate with the partitions for functions such as dynamic LPAR and Service Focal Point.
Service Agent (SA) connections: SA is the application running on the HMC for reporting hardware failures to the IBM support center. It uses a modem for dial-out connection or an available Internet connection. It can also be used to transmit service and performance information to IBM and also for CoD enablement and billing information.
Remote connection to the HMC using Web-based System Manager (WebSM) or ssh: For accessing the graphical interface, you can use the WebSM Remote Client running on UNIX® (AIX® or Linux®) or Windows®. The command line interface is also available by using the secure shell connection to the HMC. It can be used by an external management system or a partition to perform HMC operations remotely.
When planning for the HMC installation also consider that the distance between the HMC and the managed system must be within 8m (26 ft) distance. The distance complies with IBM maintenance rules.

Partitioning considerations

With POWER5 systems a greater flexibility was introduced in setting up the resources of a partition by enabling the Advanced Power Virtualization functions to provide:

POWER Hypervisor: Supports partitioning and dynamic resource movement across multiple operating system environments.
Shared processor LPAR (micro-partitioning): Enables you to allocate less than a full physical processor to a logical partition.
Virtual LAN: Provides network Virtualization capabilities that allow you to prioritize traffic on shared networks.
Virtual I/O (VIO): Provides the ability to dedicate I/O adapters and devices to a virtual server, thus allowing the on demand allocation and management of I/O devices.
Capacity on Demand (CoD): Allows system resources such as processors and memory to be activated on an as-needed basis.
Simultaneous multi-threading (SMT): Allows applications to increase overall resource utilization by virtualizing multiple physical CPUs through the use of multi-threading. SMT is a feature supported only in AIX 5.3 and Linux at an
appropriate level.
Multiple operating system support: Logical partitioning allows a single server to run multiple operating system images concurrently. On a POWER5 system the following operating systems can be installed: AIX 5L Version 5.2 ML3 or later, SUSE Linux Enterprise Server 9 Service Pack 2, Red Hat Enterprise Linux ES 4 QU1, and i5/OS.

Additional memory allocation in a partitioned environment

Three memory regions are reserved for the physical memory allocation of a partition:

Hypervisor Translation control entry (TCE) tables Partition page tables
At the beginning of a partition size planning, you have to consider that the allocated amount of memory in these three regions is not usable for the physical memory allocation of the partition.
Hypervisor and TCE
All POWER5 systems require the use of the hypervisor. The hypervisor supports many advanced functions including shared processors, Virtual I/O (VIO), high-speed communications between partitions using Virtual LAN or concurrent maintenance. There are many variables that dictate how much hypervisor memory you will need. It is not a fixed amount of memory as with POWER4 systems.
Also the amount of IO drawers and the different ways to use IO, such as shared environment, affect the amount of memory the hypervisor uses.
Note: The number of VIOs, the number of partitions, and the number of IO
drawers affect the hypervisor memory.

Partition page tables

Partition page tables are set aside in additional memory in the hypervisor to handle the partition's memory addressing. The amount of memory the partition page table reserve depends on the maximum value of the partition, and must be considered in your partition size planning.
Note: The bigger the maximum value of a partition, the bigger the amount of memory not usable for the physical memory allocation of the partition.
To calculate your desired and maximum memory values accurately, we recommend that you use the SPT tool.

HMC history

HMC code	No. of HMCs	No. of servers	No. of LPARs	Other information
4.1.x	1	4	40	iSeries Only
4.2.0	2	16	64	p5 520 550 570
4.2.1	2	32	160	OpenPower 720
4.3.1	2	32	254	p5 590 595
4.4.0	2	32	254	p5 575 HMC 7310-CR3/C04
4.5.0	2	32/48	254	48 for non 590/595
5.1.0	2	32/48	254	48 for non 590/595

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