Maximum LUN Configuration and Considerations for HP-UX

Note: The total amount of disk space that a volume group can contain is set when the volume group
is created, based on the user-specified extent size and maximum number of extents. To ease
future expansion, carefully consider the options specified at volume group creation.
File System Considerations
Due to long recovery times, HP does not recommend using HFS file systems with large numbers of
LUNs. HP recommends using the VxFS file system with large LUN levels.
Scan/Startup/Shutdown Times
As the number of LUNs increase, the time it takes to discover LUNs via ioscan or other device query
utilities increases. Because scans are done during boot, this also affects boot time. Similarly, the
number of LUNs can impact application startup times, if the applications perform an ioscan or
similar general device discovery.
To significantly reduce the ioscan time, apply the following patches (or superseding patches)
together:
Table 2: ioscan performance improvement patches
HP-UX 11.00 PHCO_27818 PHKL_24165 PHKL_24187
HP-UX 11i v1 PHCO_33136 PHKL_24163 PHKL_25165 PHKL_30257
HP-UX 11i v2 PHKL_31501
In addition, the mtIOscan11i bundle, referenced in
HP-UX 11i v1 Maximums, provides performance
improvements during the ioscan at boot time.
Topology Considerations
Using Fibre Channel arbitrated loop topologies can result in long latencies during initial device opens
when using more than 512 LUNs per HBA. To avoid this problem, HP recommends moving to Fibre
Channel fabric (switched) topologies.
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