IOSTATS(4) Kernel Interfaces Manual IOSTATS(4)
iostats - file system to measure I/O
iostats cmd [ args... ]
Iostats is a user-level file server that interposes itself between a
program and the regular file server, which allows it to gather statis-
tics of file system use at the level of the Plan 9 file system proto-
col, 9P. After a program exits a report is printed on standard error.
The report consists of three sections. The first section reports the
amount of user data in read and write messages sent by the program and
the average rate at which the data was transferred. The protocol line
reports the amount of data sent as message headers, that is, protocol
overhead. The rpc line reports the total number of file system trans-
The second section gives the number of messages, the fastest, slowest,
and average turn around time and the amount of data involved with each
9P message type. The final section gives an I/O summary for each file
used by the program in terms of opens, reads and writes.
Poor clock resolution means that large amounts of I/O must be done to
get accurate rate figures.
Can be fooled by programs that do fresh mounts outside its purview.