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# External Director metrics

Unisphere collects and displays metrics for external directors.

External Director 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 external directors.

Table 1. External Director metrics
Metric | Description
--- | ---
% Busy | The percentage of time that a director is busy
% Read Reqs | The percent of read requests out of the total requests
% Write Reqs | The percent of write requests out of the total requests
Avg Time per Syscall | The average time spent processing all system calls
Clone Copy Read | Measures, in tracks/sec, the backend read traffic that is not immediately associated to front-end I/O
Clone Copy Write | Measures, in tracks/sec, the backend write traffic that is not immediately associated to front-end I/O
IOs/sec | The number of I/Os performed each second by the director
MBs Read/sec | The number of reads per second in MBs
MBs Written/sec | The number of writes per second in MBs
MBs/sec | The total I/O (reads and writes) per second in MBs
Optimized Write | Internal metric
PHCO Rebuild Copy | Internal metric
PHCO Rebuild Read | Internal metric
Prefetched Tracks/sec | The number of tracks prefetched from disk to cache upon detection of a sequential read stream
Read Reqs/sec | A data transfer of a read between the director and the cache
Reqs/sec | A data transfer between the director and the cache - an I/O may require multiple requests depending on I/O size, alignment or both. For writes the request counter increments at the time that the write pending flag is removed from the cache slot. If multiple DAs are involved in the I/O operation (such as RAID 1), the request count may not reconcile with the I/O count and I/O size
Syscall Count/sec | The total number of calls seen by this director
Syscall RDF Dir Count/sec | The number of calls that are sent using SRDF to a remote system
Syscall Remote Dir Count/sec | The number of calls that are sent from the local director to another director in the same system
Syscall Time/sec | Total time spent processing all system calls
Write Reqs/sec | A data transfer of a write between the cache and the director