HP Surestore Disk Array FC60 HP SureStore E Disk Array 12H User's and Service - Page 107

Concepts and Management Optimizing Performance 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. Table 4. Disk Array Performance Metrics Disk Array Values: Performance Metric Typical/Limit Definition Disk Diff 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. Relocate Blocks 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. Working Set 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. Cache Utilization 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 107