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Managing Serviceguard Fifteenth Edition > Chapter 4 Planning and Documenting an HA Cluster

Hardware Planning


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Hardware planning requires examining the physical hardware itself. One useful procedure is to sketch the hardware configuration in a diagram that shows adapter cards and buses, cabling, disks and peripherals. A sample diagram for a two-node cluster is shown in Figure 4-1 “Sample Cluster Configuration ”.

NOTE: Under agile addressing, the storage units in this example would have names such as disk1, disk2, disk3, etc. See “About Device File Names (Device Special Files)”.

Figure 4-1 Sample Cluster Configuration

Sample Cluster Configuration

Create a similar sketch for your own cluster, and record the information on the Hardware Worksheet (see “Hardware Configuration Worksheet ”). Indicate which device adapters occupy which slots, and determine the bus address for each adapter. Update the details as you do the cluster configuration (described in Chapter 5). Use one form for each SPU. The form has three parts:

  • SPU Information

  • Network Information

  • Disk I/O Information

SPU Information

SPU information includes the basic characteristics of the systems you are using in the cluster. Different models of computers can be mixed in the same cluster. This configuration model also applies to HP Integrity servers. HP-UX workstations are not supported for Serviceguard.

On one worksheet per node (see “Hardware Configuration Worksheet ”), include the following items:

Server Number

Enter the series number; for example, rp8400 or rx8620-32.

Host Name

Enter the name to be used on the system as the host name.

Memory Capacity

Enter the memory in MB.

Number of I/O slots

Indicate the number of slots.

Network Information

Serviceguard monitors LAN interfaces.

NOTE: Serviceguard supports communication across routers between nodes in the same cluster; for more information, see the documents listed under “Cross-Subnet Configurations”.

Serviceguard communication relies on the exchange of DLPI (Data Link Provider Interface) traffic at the data link layer (for nodes on the same subnet) and the UDP/TCP (User Datagram Protocol/Transmission Control Protocol) traffic at the Transport layer between cluster nodes.

LAN Information

While a minimum of one LAN interface per subnet is required, at least two LAN interfaces, one primary and one or more standby, are needed to eliminate single points of network failure.

NOTE: In a cross-subnet configuration, in which the cluster spans subnets joined by a router, a standby for each subnet is required. See “Cross-Subnet Configurations” for more information.

HP recommends that you configure heartbeats on all subnets, including those to be used for client data.

Collect the following information for each LAN interface:

Subnet Name

Enter the IP address mask for the subnet. Note that heartbeat IP addresses must be on the same subnet on each node.

Interface Name

Enter the name of the LAN card as used by this node to access the subnet. This name is shown by lanscan after you install the card.

IP Address

Enter this node’s host IP address(es), to be used on this interface. If the interface is a standby and does not have an IP address, enter 'Standby.'

An IPv4 address is a string of 4 digits separated with decimals, in this form:


An IPV6 address is a string of 8 hexadecimal values separated with colons, in this form:


For more details of IPv6 address format, see the Appendix H “IPv6 Network Support”.


When there is a primary and a standby network card, Serviceguard needs to determine when a card has failed, so it knows whether to fail traffic over to the other card. The configuration file specifies one of two ways to decide when the network interface card has failed:



The default is INOUT.

See “Monitoring LAN Interfaces and Detecting Failure ” for more information.

Kind of LAN Traffic

Identify the purpose of the subnet. Valid types include the following:

  • Heartbeat

  • Client Traffic

  • Standby

This information is used in creating the subnet groupings and identifying the IP addresses used in the cluster and package configuration files.

Setting SCSI Addresses for the Largest Expected Cluster Size

SCSI standards define priority according to SCSI address. To prevent controller starvation on the SPU, the SCSI interface cards must be configured at the highest priorities. Therefore, when configuring a highly available cluster, you should give nodes the highest priority SCSI addresses, and give disks addresses of lesser priority.

For SCSI, high priority starts at seven, goes down to zero, and then goes from 15 to eight. Therefore, seven is the highest priority and eight is the lowest priority. For example, if there will be a maximum of four nodes in the cluster, and all four systems will share a string of disks, then the SCSI address must be uniquely set on the interface cards in all four systems, and must be high priority addresses. So the addressing for the systems and disks would be as follows:

Table 4-1 SCSI Addressing in Cluster Configuration

System or Disk

Host Interface SCSI Address

Primary System A


Primary System B


Primary System C


Primary System D


Disk #1


Disk #2


Disk #3


Disk #4


Disk #5


Disk #6



13 - 8


NOTE: When a boot/root disk is configured with a low-priority address on a shared SCSI bus, a system panic can occur if there is a timeout on accessing the boot/root device. This can happen in a cluster when many nodes and many disks are configured on the same bus.

The correct approach is to assign SCSI addresses in such a way that the interface cards on cluster nodes have the highest priority SCSI addresses, followed by any boot/root disks that are on the shared bus, followed by all other disks on the shared bus.

Disk I/O Information

Collect the following information for each disk connected to each disk device adapter on the node:

Bus Type

Indicate the type of bus. Supported busses are Fibre Channel and SCSI.

Slot Number

Indicate the slot number in which the interface card is inserted in the backplane of the computer.


Enter the bus hardware path number, which will be seen on the system later when you use ioscan to display hardware.

Disk Device File

Enter the disk device file name. To display the name use the ioscan -fnC disk command (for legacy DSFs) or ioscan -fnNC disk (for agile addressing).

This information is used in creating the mirrored disk configuration using Logical Volume Manager. In addition, it is useful to gather as much information as possible about your disk configuration. You can obtain information about available disks by using the following commands:

  • diskinfo

  • ioscan -fnC disk or ioscan -fnNC disk

  • lssf /dev/*dsk/*

  • bdf

  • mount

  • swapinfo

  • vgdisplay -v

  • lvdisplay -v

  • lvlnboot -v

  • vxdg list (VxVM and CVM)

  • vxprint (VxVM and CVM)

These are standard HP-UX commands. See their man pages for complete information about usage. The commands should be issued from all nodes after installing the hardware and rebooting the system. The information will be useful when doing storage group and cluster configuration. You can mark up a printed listing of the output from the lssf command to indicate which physical volume group a disk should be assigned to.

Hardware Configuration Worksheet

The following worksheet will help you organize and record your specific cluster hardware configuration. This worksheet is an example; blank worksheets are in Appendix F “Blank Planning Worksheets”. Make as many copies as you need.

   SPU Information:

    Host Name ____ftsys9___________ Series No ______rp8400____________

Memory Capacity ____128 MB _________ Number of I/O Slots ______12_______
LAN Information:

Name of Name of Node IP Traffic
Subnet __Blue___ Interface ___lan0___ Addr___35.12.16.10__ Type ____HB___

Name of Name of Node IP Traffic
Subnet __Blue___ Interface ___lan2___ Addr_______________ Type _standby_

Name of Name of Node IP Traffic
Subnet __Red____ Interface ___lan1___ Addr___35.12.15.12_ Type _HB, client

Disk I/O Information for Shared Disks:

Bus Type _SCSI_ Slot Number _4__ Address _16_ Disk Device File __________

Bus Type _SCSI_ Slot Number _6_ Address _24_ Disk Device File __________

Bus Type ______ Slot Number ___ Address ____ Disk Device File _________

Attach a printout of the output from the ioscan -fnC disk command
after installing disk hardware and rebooting the system. Mark this
    printout to indicate which physical volume group each disk belongs to.
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