HP vPars and Integrity Virtual Machines V6.1 Administrator Guide

to the virtual media are properly emulated as media errors sent to the guest OS, not as path
failures.
• The VSP does not return specific errors to Integrity VM for hardware path failures. vPars and
Integrity VM does not detect such events and does not pass them to the vPar/VM.
For supported multipathing configurations, see the HP-UX vPars and Integrity VM V6.1 Release
Notes at http://www.hp.com/go/hpux-hpvm-docs.
9.2.1.4 VM storage management
Before you decide how to divide VSP storage, consider the impact on the management of the
storage subsystem.
A VSP administrator manages VM storage to make sure virtual media is allocated safely. This
begins with understanding the VSP I/O stack and knowing from where the virtual media is being
allocated.
Figure 7 shows an example of a VSP I/O stack as it applies to a single LUN.
Figure 7 Sub-LUN Storage Allocation Example
File File File File File File File File
2 2
Logical Volume Logical Volume Logical Volume Logical Volume
Whole Disk
1
2
The virtual machine is allocated a logical volume from the LUN for a Virtual LvDisk.
• The logical volume that has been allocated is labeled 1.
• The parts of the disk that cannot be allocated are labeled 2.
Those parts that are no longer available include the files that were on the logical volume and the
whole disk that makes up part of the volume group. If any of these parts are allocated for other
virtual devices, data corruption can occur on the Virtual LvDisk.
Those parts that are still available for reallocation include other logical volumes that are on the
disk, and files that are on those other logical volumes on the disk. These pieces can be allocated
without data corruption problems because they do not overlap with the Virtual LvDisk.
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. HP-UX 11i v3 supports both legacy per-path device files (for example, /dev/rdisk/
c6t2d0) and agile non-path specific device files (for example, /dev/rdisk/disk). As shown
in Figure 8, there may be more than one legacy device file that points to the same physical storage
device, while there is only one agile device file per a given physical storage device. Use of agile
device files is recommended to avoid whole LUN collisions.
9.2 Configuring vPar/VM storage 119