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# DATA Volume metrics

Unisphere collects and displays metrics for DATA volumes.

DATA volume metrics are supported only by storage systems (arrays) running HYPERMAX OS 5977 or PowerMaxOS 5978.

The following table lists all metrics that are available for DATA volumes.

Table 1. DATA volume metrics
Metric | Description
--- | ---
Allocated Capacity (GB) | The total allocated volume capacity
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 MBs Read/sec | The number of MBs read by the disk directors from the volume each second
BE MBs Transferred/sec | Calculated value: (MBs read per sec + MBs written per sec)
BE MBs Written/sec | The number of MBs written to the volume from the disk director each second
BE Optimize Writes (MB) | Internal metric
BE Partial Sector Writes (KB) | The kilobytes of back-end I/O that were partial sector writes
BE Prefetched MBs/sec | The number of tracks per second prefetched from disk to cache upon detection of a sequential read stream
BE Prefetched Tracks Used/sec | The number of prefetched tracks used each second from the disk directors to the cache
BE Read Reqs/sec | The number of read requests each second performed by the disk directors to cache
BE Reads For Copy | Internal metric
BE Reads For Copy (KB) | Internal metric
BE Reqs/sec | The number of read/write requests each second performed by the disk directors to cache
BE Write Reqs/sec | The number of write requests each second performed by the disk directors to the cache
BE Writes For Copy | Internal metric
BE Writes For Copy (KB) | Internal metric
BE Writes For Rebuild | Internal metric
BE Writes For Rebuild (KB) | Internal metric
Device Block Size | The block size of the volume
IO Density | The number of BE requests per GB of disk
Kbytes Read for Rebuild | Kilobytes read for rebuild
Kbytes Written for IVTOC | Kilobytes written for IVTOC
Parity Generation Kbytes Read | Parity generation Kilobytes read
Reads for Rebuild | Reads for rebuild
Total Capacity (GB) | The total capacity of the volume (GBs)
WP Count | The number of tracks currently in write pending mode for the volume
Writes for IVTOC | Writes for IVTOC