HP XP Array Manager Software - Manual (Page 16)

All the statistics that can be monitored by Performance Monitor are collected and stored in
short range.
• Storing in long range
Performance Monitor collects statistics at fixed 15-minutes interval, and stores them for 3 months
(that is, 93 days).
The usage statistics about resources in the storage system are collected and stored also in long
range, in parallel with in short range. However, some of the usage statistics about resources
cannot be collected in long range.
Auto LUN window can display the statistics within the range of the storing periods above. You can specify
a part of the storing period to display the statistics on the lists and graphs of Performance Monitor.
All statistics, except some information related to Auto LUN, can be displayed in short range (for the
storing period corresponding to the setting for the collecting interval) on Auto LUN window. In addition,
usage statistics about resources in the storage system can be displayed in both short range and long
range because they are monitored in both ranges. When you display usage statistics about resources,
you can select the displayed range.
For more about statistics that can be monitored in short and long ranges, see the description of Auto
LUN window in “ Performance Monitor Window ” on page 29. For more about the relationship between
collection interval and the storing period of the statistics, see “ Monitoring Options Window ” on page 42.
Parity Group Usage Statistics
A parity group is a group of hard disk drives (HDDs) that form the basic unit of storage for the storage
system. All HDDs in a parity group must have the same physical capacity. The storage system supports
three types of parity groups as follows:
• RAID-1 parity group
A RAID-1 parity group consists of two pairs of HDDs in a mirrored configuration.
• RAID-5 parity group
A RAID-5 parity group consists of four or eight HDDs. One of these HDDs is used as a parity disk.
• RAID-6 parity group
A RAID-6 parity group consists of eight HDDs. Two of these HDDs are used as a parity disk.
If the monitor data shows overall high parity group usage, you should consider installing additional
HDDs and using Auto LUN to migrate the high-usage volumes to the new parity groups. If the monitor
data shows that parity group usage is not balanced, you can use Auto LUN to migrate volumes from
high-usage parity groups to low-usage parity groups.
For details on how to view usage statistics about parity groups, see
“ Viewing Usage Statistics about Parity Groups ” on page 50.
Volume Usage Statistics
Performance Monitor displays the average and maximum usage, including sequential and random access,
of each volume (LDEV) in a parity group. The volume usage is the time in use (sequential and random
access) of the physical drives of each LDEV, averaged by the number of physical drives in the parity group.
If the monitor data shows overall high volume usage, you should consider installing additional hardware
(for example, HDDs, DKAs, cache). If the monitor data shows that volume usage is not balanced, you
can use Auto LUN to migrate high-usage volumes to higher HDD classes and/or to lower-usage parity
groups. The volume usage data can also be used to analyze the access characteristics of volumes and
determine the appropriate RAID level and/or HDD type for the volumes.
For details on how to view usage statistics about volumes, see
“ Viewing Usage Statistics about Volumes in Parity Groups ” on page 51.
External Volume Group Usage Statistics
If the storage system is connected to an external storage system by HP StorageWorks XP External Storage
Software, Performance Monitor can also monitor the usage conditions on external hard disk drives.
16 About Performance Monitor