HP Integrity Virtual Machines Installation, Configuration, and Administration Version A.03.50

7.2.1.3 VM Storage Multipath Solutions
For load balancing and higher availability for virtual machines, consider using a multipath
solution on the VM Host. Currently there are no multipath solutions for the attachable device
types of tapes, media changers, and CD/DVD burners. However, there are several VM Host
multipath options for virtual devices.
Multipath solutions are supported on the VM Host only, not on virtual machines, for the following
reasons:
• The VM Host is the only place where all virtual I/O can be properly load balanced for the
best overall performance. A single virtual machine cannot account for all the other virtual
machine I/O with which it is competing on the VM Host (see Figure 7-1 (page 86)).
• Running a multipath solution in a virtual machine does not provide any high availability
for a virtual device. Virtual connections between virtual adapters and their devices are never
lost until an hpvmmodify command is used to disconnect them. The only connection ever
lost is the ability of a virtual device to access its own virtual media through the VM Host.
Errors in communication to the virtual media are properly emulated as media errors sent
to the guest OS, not path failures.
• The VM Host does not return specific errors to Integrity VM for hardware path failures.
Integrity VM does not detect such events and does not pass them on to the virtual machine.
Each multipath software solution for HP-UX 11.23 interacts at different layers on the I/O stack.
Since Integrity VM also interacts with different layers in the I/O stack, only certain options apply
to each virtual media type.
Table 7-1 lists the multipath solutions to use on a VM Host for each type of virtual storage media:
Table 7-1 Multipath Solutions
Multipath OptionsVirtual Media Type
EMC PowerPath
HP Autopath/Secure Path
Whole Disk
PVLinks
EMC PowerPath
HP Autopath/Secure Path
LVM Logical Volume
EMC PowerPath
HP Autopath/Secure Path
Veritas DMP
VxVM Logical Volume
PVLinks
EMC PowerPath
HP Autopath/Secure Path
Veritas DMP
VxFS File System
Although Table 7-1 lists the possible solutions for each virtual media type, it cannot determine
what is supported on your specific VM Host configuration. Each multipath solution is supported
only for specific hardware and software. The solution vendors provide this information for their
multipath products. Review the installation and release notes of these products carefully to form
a valid VM Host configuration before using it for any virtual machine. Some multipath options
do not work together and they all have different load balancing features.
7.2.1.4 VM Storage Management
Before you decide how to divide VM Host storage, consider the impact on the management of
the storage subsystem.
A VM Host administrator manages VM storage to make sure virtual media is allocated safely.
This begins with understanding the VM Host I/O stack and knowing where the virtual media is
being allocated from.
88 Creating Virtual Storage Devices