3.1.2 Matrix Server Command Reference

Chapter 1: Matrix Server Commands 25

The syntax is:

mpioload [interval [count]]

interval is the number of seconds between samplings. The default is one

second. count is the number of samples to make; the default is to sample

indefinitely.

Values for failovers and fatal errors represent the number of respective events

since the device was bound. Values for load are the instantaneous number of

I/Os queued at the time of the sample. Raw I/Os are counted as requests (calls

to read()/write()) while total (block layer) I/Os are per buffer_head structure

(i.e., call to make_request()).

Display General I/O Statistics

The iostat command displays general I/O statistics for each device. Specific

targets of PSD devices are not monitored individually. The syntax is:

iostat [interval [count]]

interval is the number of seconds between samplings. The default is one

second. count is the number of samples to make; the default is to sample

indefinitely.

The information displayed for each interval includes the number of I/Os

queued (total block and raw), minimum and maximum latency, count of I/Os,

and average latency. The statistics are organized by I/O, with only actively

used sizes shown.

Latencies are in milliseconds. The minimum and maximum latency is reset

every interval. The number of I/Os queued is an instantaneous value that is

taken at the time of the sample.

NOTE: If interval is too long, the average latency computation may be affected

by 32-bit computer wrap-around. A total of 71 minutes of I/O may be

measured before counter wrap-around. This does not necessarily

equate to 71 minutes in realtime.

Dump I/O Statistics in Raw Format

The rawstat command dumps general I/O statistics for each device in raw

format. The output is typically passed to programs or shell scripts for further