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# Disk Group metrics

Unisphere collects and displays metrics for disk groups.

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 disk groups.

Table 1. Disk group 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 group capacity that is allocated.
Avg Read Size (KB) | Calculated value: (Kbytes read per sec/total reads per sec)
Avg Write Size (KB) | Calculated value: (Kbytes written per sec/total writes per sec)
IO Density | The number of BE requests per GB of disk
IOs/sec | The number of I/O commands to 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 Block Read/sec | The rebuild blocks read per second (V4)
Rebuild Blocks Written/sec | The rebuild blocks written per second (V4)
Response Time | The average response time for the reads and writes
Spare Hypers Count | The spare hypers count (V4)
Throughput | The total I/O (reads and writes) per second in MBs
Throughput Read | The average throughput of host MBs read (per second) by the director
Throughput Written | The average throughput of host MBs written (per second) by the director
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 | The 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