HP Integrity Virtual Machines Installation, Configuration, and Administration

Beyond avoiding sub-LUN collisions, whole LUN collisions also need to be avoided. The same
storage resource, virtual or attached, cannot be specified more than once to the same virtual
machine. Under HP-UX 11.23, most storage device files are defined per path. Be careful not to
specify a given device twice. Figure 7-4 shows an example of two device files,
/dev/rdsk/c6t2d0 and /dev/rdsk/c11t2d0 pointing to the same physical disk. Once the
/dev/rdsk/c6t2d0 device file is specified for a Virtual Disk, the /dev/rdsk/c11t2d0 device
file is no longer available.
Figure 7-4 Bad Multipath Virtual Media Allocation
Physical
Adapter
Physical
Adapter
Physical
Storage
/dev/rdsk/c6t2d1 /dev/rdsk/c11t2d1
Also, the same storage resource, virtual or attached, cannot be simultaneously shared between
virtual machines, unless otherwise specifically exempted. Figure 7-5 shows a Virtual LvDisk
being shared across virtual machines, which is not supported.
Figure 7-5 Bad Virtual Device Allocation
Guest A Guest B
Virtual
LvDisk
As these examples illustrate, it is important to know where storage is allocated from to avoid
data corruption with virtual machines or even the VM Host. Management utilities such as HP
System Administration Manager (sam) and the System Management Homepage (SMH) utilities
allow you to track disk devices, volume groups, logical volumes, and file systems. You can use
these utilities to annotate devices so that VM Host administrators can see exactly which virtual
machines are using each VM Host storage device.
To show each disk only once, management utilities consolidate multipath devices into one disk.
When you are dividing up the disk, you should use all the parts of a single disk on a single virtual
machine. Allocating different parts of the same disk to different virtual machines makes it difficult
to manage and to isolate problems.
7.2.1.5 VM Storage Changes
Depending on how you set up storage for a virtual machine, the resulting configuration can be
more or less difficult to change.
The ability to change virtual media depends on the type of virtual media used. Whole disks are
not normally adjustable in terms of size, but some high-end storage enclosures may permit the
adjustment of a LUN without losing that LUN's data. Logical volumes are adjustable without
losing any data. Finally, files can be changed easily with VM Host file system commands.
7.2 Configuring Integrity VM Storage 79