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HACMP supports Virtualization (VLAN/VSCSI)

Document Author:

Michael E Herrera

Document ID:


Doc. Organization:

Advanced Technical Sales

Document Revised:


Product(s) covered:

HACMP/ES; Power5; pSeries

Abstract: HACMP supports Virtualization, including VLAN and VSCSI.

HACMP and Virtualization
This document outlines the supported configurations for use of HACMP with the IBM virtualization features Virtual LAN and Virtual SCSI.

Software Requirements


AIX 5L v5.3 Maintenance Level 5300-002 with APAR IY70082 and iFIX IY72974
  • APAR IY70082 is available at:

VIO Server

VIO Server v1.1 with VIOS Fixpack 6.2 and iFIX IY71303.062905.epkg.Z
  • Fixpack 6.2 and iFIX IY71303.062905.epkg.Z are available at:


HACMP v5.1 with APAR IY66556 (or higher)
HACMP v5.2 with APAR IY68370 (or higher) and APAR IY68387
HACMP v5.3

These APARs are available at:

RSCT (Reliable Scalable Cluster Technology)

The following RSCT filesets are required:
  • rsct.basic.hacmp
  • rsct.basic.rte.
  • rsct.compat.basic.hacmp.

These filesets are available at:

HACMP and Virtual SCSI (vSCSI)
  • The volume group must be defined as “Enhanced Concurrent Mode.” In general, Enhanced Concurrent Mode is the recommended mode for sharing volume groups in HACMP clusters because volumes are accessible by multiple HACMP nodes, resulting in faster failover in the event of a node failure. If file systems are used on the standby nodes, they are not mounted until the point of failover so accidental use of data on standby nodes is impossible. If shared volumes are accessed directly (without file systems) in Enhanced Concurrent Mode, these volumes are accessible from multiple nodes so access must be controlled at a higher layer such as databases.
  • If any cluster node accesses shared volumes through vSCSI, all nodes must do so. This means that disks cannot be shared between an LPAR using vSCSI and a node directly accessing those disks.
  • From the point of view of the VIO server, physical disks (hdisks) are shared, not logical volumes or volume groups.
  • All volume group construction and maintenance on these shared disks is done from the HACMP nodes, not from the VIO server.

HACMP and Virtual Ethernet
  • IP Address Takeover (IPAT) via Aliasing must be used. IPAT via Replacement and MAC Address Takeover are not supported. In general, IPAT via Aliasing is recommended for all HACMP networks that can support it.
  • HACMP’s “PCI Hot Plug” facility cannot be used. PCI Hot Plug operations are available through the VIO Server. Note that when an HACMP node is using Virtual I/O, HACMP’s “PCI Hot Plug” facility is not meaningful because the I/O adapters are virtual rather than physical.
  • All Virtual Ethernet interfaces defined to HACMP should be treated as “single-adapter networks” as described in the Planning and Installation Guide. In particular, configure the to include a list of clients to ping, must be used to monitor and detect failure of the network interfaces. Due to nature of Virtual Ethernet, other mechanisms to detect the failure of network interfaces are not effective.

Further configuration-dependent attributes of HACMP with Virtual Ethernet
  • If the VIO server has multiple physical interfaces on the same network or if there are two or more HACMP nodes using VIO servers in the same frame, HACMP will not be informed of (and hence will not react to) single physical interface failures. This does not limit the availability of the entire cluster because VIOS itself routes traffic around the failure. The VIOS support is analogous to EtherChannel in this regard. Other methods (not based the VIO server) must be used for providing notification of individual adapter failures.
  • If the VIO server has only a single physical interface on a network then a failure of that physical interface will be detected by HACMP. However, that failure will isolate the node from the network.

Although some of these may be viewed as configuration restrictions, many are direct consequences of I/O Virtualization.


Hardware; Software


Planning and Design


IBM System p Family




hacmp, vio, vscsi, vlan, hacmp/es, micro, partition

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