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disk busy I/O

moham_1
Occasional Contributor

disk busy I/O

how can i determine if the the total number of disk transfers for systemconsumed the most disk transfers by scale , in other words "when it considered as a high "
3 REPLIES
Alzhy
Honored Contributor

Re: disk busy I/O

If you're using HPUX:

You can use SAM.

You can use IOSTAT too.

But your best friend is to use SAR ("sar -d 5 100)

If your pockets are deep, invest on installing GlancePlus software.

If using Windows, then use the perf tools relating to disk available to you.

Hakuna Matata.
Stuart Abramson_2
Honored Contributor

Re: disk busy I/O

Things to look for in sar -d are:

a. % busy greater than 50%

b. avque greater than 3

c. avwait greater than avserv.

- This means the i/os are waiting longer than the
the time it takes to process them. Bad...

d. However:

- %busy high and queue length low, is okay, because
it means the disk is working, but is keeping up.

e. avserv < 6 ms is good!

If a disk rotates at 10,000 revolutions per minutes, then
how long does one revolution take:

10,000 revolutions
10,000 RPM = ------------------
60 seconds

60 seconds
1 revolution = --------------
10,000

= .006 seconds

= 6 milliseconds

f. Average seek time would be 1/2 rotation time. Also
called "latency time".

g. Average transfer rate for one block of data on one
cylinder would then be 6 milliseconds.


moham_1
Occasional Contributor

Re: disk busy I/O

thanx capparroso & abramson ,


if the average disk I/O is about 30K ,
does it requires any upgrade or change ?




attached a graph from OVO/OVR to know your opinion .

regards