topic What is I/O Wait in Operating System - HP-UX

What is I/O Wait

Sagar Sirdesai — Tue, 17 Aug 2010 05:02:17 GMT

Hi All,
I need whether I/O Wait is a Measure of CPU Utilization or Idle Time.

Sagar

Re: What is I/O Wait

Wim Rombauts — Tue, 17 Aug 2010 05:38:20 GMT

I/O Wait is the time the CPU is doing nothing because all processes it could work on are waiting for I/O operatons to complete.

So, there is no CPU utilization, but it's not idle time either.

Re: What is I/O Wait

Ricky_HK — Tue, 17 Aug 2010 08:26:53 GMT

idle + iowait = total idle time

Re: What is I/O Wait

muruganantham raju — Wed, 18 Aug 2010 03:50:44 GMT

Hi Sagar,
I/O wait is accounted for idle time.

To find out CPU IDLE % in your system, run the sar command.

e.g.

# sar -u 1 2

HP-UX biavm4-3 B.11.23 U ia64 08/18/10

04:47:47 %usr %sys %wio %idle
04:47:48 0 0 0 100
04:47:49 0 0 0 100

Total Idle% = %wio + %idle

Regards,
Muru

Re: What is I/O Wait

Hakki Aydin Ucar — Wed, 18 Aug 2010 07:26:01 GMT

Hi,
%wio - idle with some process waiting for I/O ;

related with Disks that was busy with another process before..

Re: What is I/O Wait

Hakki Aydin Ucar — Wed, 18 Aug 2010 07:50:11 GMT

Also check these out:

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=62143

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1086719

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=138987

http://h21007.www2.hp.com/portal/download/files/unprot/devresource/Docs/TechPapers/UXPerfCookBook.pdf

Re: What is I/O Wait

Sagar Sirdesai — Mon, 23 Aug 2010 15:08:57 GMT

Thanks to all for their replies