HP XP Array Manager Software - Manual (Page 17)

When you use External Storage to map the volumes in the external storage system as volumes in the
storage system, the mapped volumes in the external storage system are called external volumes. These
external volumes are registered in groups by External Storage. Performance Monitor can monitor the
usage conditions for external volume groups.
Note: An external volume group is just a group for managing external volumes. Unlike a parity group, it
does not contain any parity information. However, some windows of Performance Monitor treat external
volume groups same as parity groups for convenience.
The information that can be monitored about an external volume group differs from that of a usual
parity group. For details on how to view usage conditions about external volume groups, see
“ Viewing Usage Statistics about External Volume Groups ” on page 53.
External Volume Usage Statistics
An external volume is a volume existing in an external storage system that is mapped to a volume in
the storage system using External Storage. Performance Monitor can monitor and display the usage
conditions for external volumes.
The information that can be monitored for an external volume differs from that of a
typical volume. For details on how to view usage conditions about external volumes, see
“ Viewing Usage Statistics about External Volumes in External Volume Groups ” on page 54.
Channel Processor Usage Statistics
A channel processor (CHP), which is contained in a channel adapter (CHA), processes host commands
and controls data transfer between hosts and the cache. A channel adapter contains multiple channel
processors that process host commands and control data transfer.
If monitoring data shows high overall CHP usage, you should consider installing additional CHAs. If
monitoring data shows that CHP usage is not balanced, you should consider moving some devices that
are defined on overloaded ports to ports with lower-usage CHPs to balance front-end usage.
For details on how to view usage statistics about channel adapters and channel processors groups, see
“ Viewing Usage Statistics about Channel Processors (CHPs) ” on page 55.
Note: A channel adapter can also be called port controller.
Disk Processor Usage Statistics
A disk processor (DKP), which is contained in a disk adapter (DKA), controls data transfer between the
cache and the disk devices. A disk adapter contains multiple disk processors (DKPs).
If monitor data shows high DKP usage overall, you should consider installing additional HDDs and/or
DKAs, and then using Auto LUN to migrate the high-write-usage volumes (especially sequential writes) to
the new parity groups. If the monitor data shows that DKP usage is not balanced, you can use Auto LUN
to migrate volumes from high-usage parity groups to low-usage parity groups.
When you consider migrating volumes from one parity group to another, take the following steps:
1. See Table 2 on page 18 to determine the parity groups from which you want to migrate volumes.
2. Check the usage rate of each parity group to find parity groups whose usage rate is lower
than the parity groups that you want to migrate. It is recommended you migrate volumes from
higher-usage parity groups to lower-usage parity groups.
XP24000 Performance Monitor User's Guide 17