HP Integrity Virtual Machines 4.3: Installation, Configuration, Administration

Figure 6-5 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 the
HP System Management Homepage (HP SMH) utility 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.
When an LVM volume group is deactivated, the storage (physical volumes) used by that storage
is designated as unused by HP-UX system administration tools such as System Management
Homepage (SMH). This is also true for Integrity VM storage management. As a result, these
physical volumes are not automatically protected from use by virtual machines as virtual disks.
You can resolve this problem in one of two ways:
• If the volume group is to remain deactivated, the VM Host administrator can manually add
the physical volume as a restricted device with the hpvmdevmgmt command.
• Or, after activating the volume group, execute the hpvmhostrdev command, so that the
VM Host storage management database is updated accordingly.
An HP-UX system administrator can deactivate a volume group using the vgchange command.
It can also be deactivated, if it is a shared LVM (SLVM) volume group, whenever the associated
Serviceguard cluster is reconfigured, or the VM Host system is rebooted. Take care to check that
all SLVM volume groups are activated after a VM Host reboot or Serviceguard cluster
reconfiguration.
6.2.1.5 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 might 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.
No changes to any virtual media can take place on the VM Host until the virtual device that uses
the media is removed from the active VM. Attempts to change virtual devices that have I/O
active on them is denied by the hpvmmodify command. Once an active virtual machine is
allocated virtual media for a virtual device, that virtual machine owns that media and can access
it any time. VM Host administrators need to coordinate with VM guest administrators about
active virtual machine changes, if the two roles are served by different individuals.
This coordination might also be necessary for attached I/O devices. Once a VM Host device is
attached to the virtual machine, it is controlled and owned by that virtual machine. Modifications
100 Creating Virtual Storage Devices