IBM Books

Planning Volume 2, Control Workstation and Software Environment

Related options and limitations for control workstations

Some configuration options that can make your control workstation more available are separate from the high availability control workstation program. They include disk mirroring, uninterruptible power supplies, and dual disk controllers both internal and external. You must also be aware of any frame supervisor changes, HACWS limits and restrictions, and complete the related HACMP planning worksheets.

Uninterruptable power supply

An uninterruptable power supply can supply electricity to a device to keep it running when main power is interrupted or is unreliable. Usually an uninterruptible power supply is not the sole source of power. Rather, it is typically used to smooth a fluctuating source or to provide enough power to enable a device to shut down gracefully. You can use an uninterruptible power supply in conjunction with all other means of assuring control workstation reliability. See the RS/6000 General Services Document Site and Hardware Planning Information for the power consumption requirements of your control workstation.

Power independence

Each control workstation should be attached to a different electrical power source or breaker panel if possible. They should at least be on separate circuits so that maintenance or failures in main power can affect only one control workstation.

Single control workstation with disk mirroring

The process of mirroring occurs when each block of data written to one disk is also written to another disk. You always have a copy of your data in case one disk or disk adapter fails. As a middle ground to availability you can decide to have a single control workstation and mirror the root volume group to provide better availability of the control workstation. This involves two or three times the number of disks needed for the root volume group, depending on whether you want one or two mirrors of the original. See the discussion on mirroring in the book AIX System Management Guide: Operating System and Devices. That book describes the AIX support for mirroring root volume groups. See the book PSSP: Administration Guide for additional SP-specific support of mirroring root volume groups.

Spare Ethernet adapters

You can cable spare SP Ethernet adapters into the existing Ethernet LAN segments for the SP and leave them in a defined but unavailable configuration state. When an Ethernet adapter fails, you can unconfigure the failing adapter and configure the spare Ethernet adapter for that LAN segment. You can use the spare adapter until the failed one is repaired or replaced. Note that the spare Ethernet adapter still counts as one of the stations in the 30 total stations you can have on an Ethernet LAN segment.

Frame supervisor changes

Check with your IBM representative for information about ordering the necessary hardware.

Limits and restrictions

The high availability control workstation support has the following limitations and restrictions:

|HACWS is not supported in any configuration of clustered enterprise |servers. HACWS is also not supported in SP systems with SP-attached |servers that use the CSP or HMC hardware protocol. Generally, it is not |a good idea to run HACWS on systems with SP-attached servers.

|However, if you already have HACWS running on your SP system, have |reasoned that you cannot do without HACWS, accept all the limitations, have |specialized experience, and can implement your own manual intervention |procedures for fail over, you might be able to make HACWS continue to work in |your SP system with SP-attached servers that use the SAMI hardware |protocol. IBM e(logo)server pSeries 680 and RS/6000 Enterprise Servers |S70, S7A, and S80 connect to the control workstation by two serial |connections, making them SP-attached servers in an SP system. One |connection is for hardware monitoring and control and the other is for serial |terminal support. These servers use the SAMI hardware protocol for |those connections. Only one control workstation at a time can be |connected to each server, so there cannot be automatic physical failover done |by the HACWS software. When the primary control workstation fails over |to the backup control workstation, hardware control and monitoring support and |serial terminal support are not available for these servers.

The following apply if you use high availability control workstation support with |SAMI protocol RS/6000 or pSeries servers in an SP-attached or clustered enterprise server configuration:

|For a list of the monitoring and control functions that might be |lost depending on your server hardware, see the discussion of SP-attached and |clustered enterprise servers in the HACWS chapter of the book PSSP: |Administration Guide.

Completing planning worksheets for HACWS

You will have to complete the following worksheets in the HACMP documentation:

As you complete the HACMP planning and installation steps, take the Non-Concurrent option whenever you are given the choice.

See the book HACMP: Planning Guide, for complete planning information.

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