HP StorageWorks XP Remote Web Console Software - Manual (Page 12)

Table 1 HCD Settings for Static and Dynamic Compatible PAV
Dynamic Alias Algorithm in Effect I/O Priority Management Dynamic Alias Support
None (that is, static Compatible PAV only) NO NO
None (that is, static Compatible PAV only) YES NO
Efficiency only NO YES
Both efficiency and goal YES YES
Static Compatible PAV
When static Compatible PAV is used, the number of aliases specified for each base device does
not change, even when the number of I/O requests to each device changes. When dynamic
Compatible PAV is used, the number of aliases for each base device is likely to change as the
number of I/O requests changes.
Figure 3 (page 12) shows an example of static Compatible PAV operations. Each of the three base
devices (x10, x11, x12) has two aliases assigned. If I/O requests converge on base device x10
(shown by the large arrow), the number of aliases for each base device remains unchanged.
If you will be using static Compatible PAV, you need to determine on which devices I/O requests
are likely to converge, and then assign more aliases to those base devices. If not, Compatible PAV
might not be able to provide much improvement in host access to data in the storage system.
Figure 3 Static Compatible PAV
Dynamic Compatible PAV
When dynamic Compatible PAV is used, the number of aliases for a base device may change as
the number of I/O requests to the device changes. If I/O requests converge on several base devices,
the number of aliases for these devices may increase, while the number of aliases for other base
devices may decrease. Dynamic Compatible PAV operations can balance workloads on base
devices and optimize the speed for accessing data in the storage system.
Figure 3 (page 12) shows an example of dynamic Compatible PAV operations. Each of the three
base devices (x10, x11, x12) was originally assigned two aliases. In this example, as I/O requests
converge on base device x10 (shown by the large arrow), the number of aliases for device x10
increases to four, while the number of aliases for base device x11 and x12 decreases to one.
Dynamic Compatible PAV operations require the Workload Manager (WLM) software function
provided by the host computer. For further information on WLM operations, see
“WLM Host
12 About Compatible PAV Operations