Michael E Herrera
Advanced Technical Sales
|Abstract: Announcement of HACMP support for IBM VIO Server v1.4 |
HACMP supports the IBM VIO Server v1.4
August 10, 2007
IBM* High Availability Cluster Multiprocessing (HACMP*) for AIX 5L*, Versions 5.2, 5.3, and 5.4 extends support to include IBM Virtual I/O Server (VIO Server) Version 1.4 virtual SCSI and virtual Ethernet devices on all HACMP supported IBM POWER5* and POWER6* servers along with IBM BladeCenter JS21. This includes HACMP nodes running in LPARs on supported IBM System i5* processors.
Please refer to the following table for support details.
Note: TL = Technology Level (Minimum)
**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 HACMP Planning and Installation Guide. In particular, configure the netmon.cf to include a list of clients to ping, must be used to monitor and detect failure of the network interfaces. Due to the 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 one or more VIO Servers in the same frame, HACMP will not be informed of (and hence will not react to) individual physical interface failures. This does not normally limit the availability of the entire cluster because VIOS itself routes traffic around individual failures. The VIOS support is analogous to EtherChannel in this regard. Even in the extreme case where all physical interfaces managed by VIO Servers have failed, the VIOS will continue to route traffic from one LPAR to another in the same frame, and the virtual ethernet interface used by HACMP will not be reported as having failed and HACMP will not react. Other methods (based on the VIO Server and not HACMP) 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.
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