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# Disk metrics

Unisphere collects and displays metrics for disks.

Within the PM metrics section, V4 is used to denote that the metric is supported only by a storage system (array) running PowerMaxOS 10 (6079). V3 is used to denote that the metric is supported only by a storage system (array) running HYPERMAX OS 5977 or PowerMaxOS 5978. Metrics without the denotation are supported by all storage systems (arrays).

The following table lists all metrics that are available for disks.

Table 1. Disk metrics
Metric | Description
--- | ---
% Busy | The percentage of time that the disk is busy serving I/Os
% Free Capacity | The percentage of the disk that is free
% Idle | The percentage of time the disk is idle
% Used Capacity | The percentage of the disk that is used
Avg Queue Depth | Calculated value: Accumulated queue depth/total SCSI command per sec
Avg Read Size | The average number of kilobytes for a single read command
Avg Write Size | The average number of kilobytes for a single write command
IOs/sec | The number of host read and write requests for the disk
Read RT | The average time that it took the disk to serve one read command
Reads/sec | The number of host reads per second for the disk
Rebuild Blocks Read | The rebuild blocks read (V4)
Rebuild Blocks Written | The rebuild blocks written (V4)
Response Time | The average response time for the reads and writes
Spare Hypers Count | The spare hypers count (V4)
Throughput | The size of the I/O from the host to the disk per second
Throughput Read | The read throughput (MBs) of the disk per second
Throughput Written | The write throughput (MBs) of the disk per second
Total Capacity | The total capacity of the disk (GBs)
Total SCSI Commands/sec | The total number of read commands, write commands, skip mask commands, verify commands, XOR write commands, and XOR write-read commands performed by the disk each second
Unmap Command Count | Unmap command count
Used Capacity | The total used capacity of the disk (GBs)
Write RT | The average time that it took the disk to serve one write command
Writes/sec | The number of host writes per second for the disk