topic Re: Disk BottleNeck in Operating System - HP-UX

Disk BottleNeck

deepak_9 — Fri, 11 Jan 2002 04:19:46 GMT

Hi Experts,

Getting an error saying :-
<<
"Disk Bottleneck Probability=100% , End of Disk Bottleneck Alert".
>>
in my GlancePlus. I wanted to know what does this alert mean and how critical it is, what are the measures to take care of?

Re: Disk BottleNeck

Craig Falls — Fri, 11 Jan 2002 04:31:44 GMT

Hi,

Basically GlancePlus has an "expert system" embeded in it which when the various aspects of performance drop check the things affecting performance and provide a somewhat informed decision about what is causing this performance drop. In the instance here GlancePlus is 100% sure that it's a disk bottleneck.

If you have a look at the /var/opt/perf/advisor.syntax file you can have a look at the way GlancePlus determines bottlenecks.

Now for criticality - well if you platform is like this ALL the time this is a critical problem. If it is only like this during specific jobs - can these jobs be rescheduled?

Measures to take care of it could range from newer faster disks/different storage technology (from internal SCSI disks to external fibre connected Array disks)

Before you can measure how critical it is and what needs to happen you really need to isolate what is running at the time the disk bottlenecks occur.

c

Re: Disk BottleNeck

Craig Falls — Fri, 11 Jan 2002 05:03:09 GMT

Sorry my mistake, in the above I wrote that the information that GlancePlus displays comes from /var/opt/perf/advisor.syntax, well this is correct but the alarms are actually defined in /var/opt/perf/alarmdef .

c

Re: Disk BottleNeck

Tom Geudens — Fri, 11 Jan 2002 05:13:18 GMT

Hi,
I don't know whether or not you already use it, but http://h21007.www2.hp.com/dspp/files/unprotected/devresource/Docs/TechPapers/UXPerfCookBook.pdf is a "must read" for bottleneck issues. I'm "fighting" an IO-bottleneck at this very moment too and this document is helping me along ... and it reads like a novel too :-) !

Hope this helps,
Tom Geudens

Re: Disk BottleNeck

Sanjay_6 — Fri, 11 Jan 2002 06:09:10 GMT

Hi Deepak,

Try this tuning guide,

http://docs.hp.com/hpux/onlinedocs/os/11.0/tuningwp.html

Hope this helps.

Regds

Re: Disk BottleNeck

T G Manikandan — Fri, 11 Jan 2002 06:13:39 GMT

Hello,
This message is due to the I/O on the disk.
There is more read/write operations on the disk.
When these operations reach the maximum the performance monitor shoots this message.

check out the disk on which there is 100% disk I/O.
It is quite possible when you have lot of applications writing onto the same disk like oracle.
Distribute your application into various disks so that the I/O is also distributed for better performance.

Thanks