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# Device group metrics

Unisphere collects and displays metrics for device 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 device groups.

Table 1. Device group metrics
Metric | Description
--- | ---
% Hit | The percentage of I/O operations that were immediately satisfied from cache
% Miss | The percentage of I/O operations that were misses
% Random IO | The percentage of I/O operations that were random
% Random Read Hit | Calculated value: 100 * (random read hits per sec/total I/Os per sec)
% Random Read Miss | Calculated value: 100 * (random read misses per sec/total I/Os per sec)
% Random Reads | The percentage of all read I/Os that were random.
% Random Write Hit | Calculated value: 100 * (random write hits per sec/total I/Os per sec)
% Random Write Miss | Calculated value: 100 * (random write misses per sec/total I/Os per sec)
% Random Writes | The percentage of all write I/Os that were random
% Read Hit | The percentage of read operations, performed by the group, that were immediately satisfied by cache.
% Read Miss | The percentage of read miss operations performed each second by the group. A miss occurs when the requested read data is not found in cache.
% Reads | The percentage of I/O operations that were reads
% Seq Read | Calculated value: 100 * (seq reads per sec/total I/Os per sec)
% Seq Read Hit | The percentage of the sequential read operations that were immediately satisfied from cache.
% Seq Read Miss | The percentage of the sequential read operations that were misses.
% Seq Write Hit | The percentage of the sequential write operations that were immediately satisfied from cache.
% Seq Write Miss | The percentage of the sequential write operations that were misses.
% Seq Writes | Calculated value: 100*(seq writes per sec/total I/Os per sec)
% Sequential IO | Calculated value: 100 * (total seq I/Os per sec/total I/Os per sec)
% Write Hit | The percentage of write operations, performed by the group, that were immediately satisfied by cache.
% Write Miss | The percentage of write miss operations performed each second by the group. A miss occurs when the write operation had to wait while data was destaged from cache to the disks.
% Writes | The percentage of I/O operations that were writes
Allocated Capacity | The allocated capacity of the device group
Avg IO Size | Calculated value: (HA Kbytes transferred per sec/total I/Os per sec)
Avg Read Size | Calculated value: (Kbytes read per sec/total reads per sec)
Avg Write Size | Calculated value: (Kbytes written per sec/total writes per sec)
Avg. Write Paced Delay (ms) | Average write paced delay (milliseconds) (V3)
BE % Reads | The percent of the back-end I/O that were read requests.
BE % Writes | The percent of the back-end I/O that were write requests.
BE Optimize Write Throughput | Internal metric
BE Partial Sector Writes (KB) | The kilobytes of back-end I/O that were partial sector writes (V3)
BE Prefetched Throughput | The number of MBs prefetched from disk to cache in a second.
BE Prefetched Tracks Used/sec | The number of prefetched tracks used each second from the disk directors to the cache
BE Prefetched Tracks/sec | The total prefetched tracks each second from the disk directors to the cache
BE RDF Copy Throughput | Internal metric
BE RDF Copy/sec | Internal metric
BE Read Reqs/sec | The number of read requests each second performed by the disk directors to cache
BE Read Throughput For Copy | BE Read Throughput For Copy
BE Reads For Copy/sec | Internal metric
BE Reqs/sec | The number of read/write requests each second performed by the disk directors to cache.
BE Throughput Read | BE Throughput Read
BE Throughput Transferred | BE Write Throughput Transferred
BE Throughput Written | BE Throughput Written
BE Write Reqs/sec | The number of write requests each second performed by the disk directors to cache.
BE Write Throughput For Copy | BE Write Throughput for copy
BE Write Throughput For Rebuild | BE Write Throughput for rebuild
BE Writes For Copy/sec | Internal metric
BE Writes For Rebuild/sec | Internal metric
Device Block Size | The block size of the volume
Host Hits/sec | The number of host read/write operations performed each second by the group that were immediately satisfied from cache.
Host lOs/sec | The number of host operations performed each second by the group.
Host Misses/sec | The number of host read/write operations performed each second by the group that could not be satisfied from cache.
Host Read Hits/sec | The number of host read operations performed each second by the group that were immediately satisfied from cache.
Host Read Misses/sec | The number of host read operations performed each second by the group that were not satisfied from cache.
Host Reads/sec | The number of host read operations performed each second by the group.
Host Throughput | The cumulative number of host MBs read/writes per second by the group.
Host Throughput Read | The cumulative number of host MBs read per second by the group
Host Throughput Written | The cumulative number of host MBs written per second by the group
Host Write Hits/sec | The number of host write operations performed each second by the group that were immediately satisfied from cache.
Host Write Misses/sec | The number of host write operations performed each second by the group that were not satisfied from cache.
Host Writes/sec | The number of host write operations performed each second by the group.
IO Density | The number of BE requests per GB of disk.
Max WP Threshold | The maximum number of write-pending slots available for the group
Random IOs/sec | I/Os from a host that is not identified as part of a sequential stream
Random Read Hits/sec | Random read I/O that were satisfied from the cache
Random Read Misses/sec | Random read I/O that were misses
Random Reads/sec | Read I/O commands from a host that is not identified as part of a sequential stream.
Random Write Hits/sec | Random write I/Os that were immediately placed in cache because space was available
Random Write Misses/sec | Random write I/Os that were misses
Random Writes/sec | Write I/O commands from a host that is not identified as part of a sequential stream.
RDF Reads/sec | Total SRDF reads per second for the device group.
RDF Response Time | The SRDF round-trip time - the metric is calculated as follows: SRDF Accumulated Service Time/(SRDF Reads/sec + SRDF Writes/sec) rolled up from the SRDF devices in the group
RDF Rewrites/sec | SRDF rewrites per second
RDF MBs Read/sec | SRDF MBs reads per second
RDF Throughput Read | SRDF MBs written per second
RDF Throughput Written | Total SRDF writes per second for the device group.
RDF/S Write RT | A summary of the read, write, and average response times for the selected SRDF/S group.
Read Miss RT | The average time that it took the storage system to serve one read miss I/O for this group.
Read RT | The average time that it took the storage system to serve one read I/O for this group.
Response Time | The average time that it takes to satisfy I/O requests.
Seq lOs/sec | Number of I/O operations performed each second that were sequential.
Seq Read Hits/sec | Number of sequential read operations performed each second by the group that were immediately satisfied from cache.
Seq Read Miss/sec | Number of sequential read operations performed each second by the group that were misses
Seq Reads/sec | Number of read I/O operations performed each second that were sequential.
Seq Write Hits/sec | Number of sequential write operations performed each second by the group that were immediately satisfied from cache.
Seq Write Misses/sec | Number of sequential write operations performed each second by the group that were misses.
Seq Writes/sec | Number of write I/O operations performed each second that were sequential.
Total Capacity | The total capacity of the device group
WP Count | The number of tracks currently in write pending mode for the group.
WP Used Capacity | The WP used capacity
Write Miss RT | The average time that it took the storage system to serve one write miss I/O for this group.
Write Paced Delay (ms) | Write paced delay (milliseconds) (V3)
Write RT | The average time that it took the storage system to serve one write I/O for this group