Performance Metrics - HP Surestore Disk Array 12h - And FC60 Service Manual

Performance Metrics

As shown in Table 4, the disk array uses an internal set of metrics to monitor its own performance. These
metrics reflect internal events and conditions that are continually measured and stored by the disk array. A
host disk array management utility can access the metrics and use them to evaluate performance, and even
make recommendations on how to improve performance. For more information on accessing the
performance metrics, refer to your operating system documentation.
Disk Array
Performance Metric
Disk Diff
Relocate Blocks
Working Set
Cache Utilization
Table 4. Disk Array Performance Metrics
Values:
Typical/Limit
0–1/>1 Indicates if the disks are properly distributed across
the internal SCSI channels. If the disks are not
installed properly, one of the SCSI channels may be
handling more than its share of activity, reducing
performance. Redistributing the disks will solve this
problem.
For more information, see SCSI Bus Topology.
0.008/>0.07 Indicates how much data is being moved between
RAID 0/1 and RAID 5. If too much data is being
transferred between RAID 0/1 and RAID 5,
performance declines.
1/>1.1 Indicates the ratio of the write working set to the
amount of RAID 0/1 space available. To maintain
performance, the amount of RAID 0/1 space should
equal or exceed the write working set (a value of 1 or
less). A value greater than 1 indicates that the working
set is larger than the available RAID 0/1 space. In this
case, the disk array must service writes from RAID 5
space, which degrades performance.
For more information, see Write Working Set.
0.1/0.2 Indicates how efficiently the write cache on the disk
array controller is being utilized. If the write cache is
consistently full, too many commands begin stacking
up in the cache queue, resulting in decreased
performance.
Concepts and Management
Optimizing Performance
Definition
107