SAR (IO)

To monitor the disk usage

# sar -d 10 5

The o/p has the following columns

%busy- The portion of time the device was busy servicing a transfer request.
avque - The average number of requests in queue.
r+w/s- Number of read and write requests per second.
Kbs/s - The number of Kbytes transferred per second.
avwait- The average time each request waits in the queue before it is serviced.
avserv- The average time taken for servicing a request.

Inference

• %busy > 50 on a device indicates contention.
• Avwait should not be greater than avserv
• A high %busy and high avque indicates a big I/O bottleneck.

Thanks