Explanation on iostat linux command

Hi Guru's

I would like to ask regarding the iostat command. Can anyone explain to me what does rrqm/s, wrqm/s, r/s, w/s, etch... mean?

Also, how do I know if there is a io load issue on hard disk?
SandManAsked:
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farzanjCommented:
rrqm/s    The number of read requests merged per second  that  were issued to the device.
 wrqm/s  The  number of write requests merged per second that were  issued to the device.
 r/s         The number of read  requests  that  were  issued  to  the  device per second.
 w/s        The  number  of  write  requests  that were issued to the  device per second.
 rsec/s     The number of sectors read from the device per second.
wsec/s  The number of sectors written to the device per second.

This link should be useful too.
http://www.cyberciti.biz/tips/linux-disk-performance-monitoring-howto.html
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SandManAuthor Commented:
Hi Farzanj,

Many thanks for the info, so i read the link it says " if a hard disk reports consistently high reads/writes " there is some high load issues on a hard disk.

Now my question, how do i distinguish, if it's a high, average or low?

From what I understand, 1+ cpu load is acceptable, above that like 2.+ is considered quite high.

please correct me if i'm wrong
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SandManAuthor Commented:
anyone guys?
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JRoyseCommented:
You would have to compare the throughput on the IO device with what the current status is.

For example if you had one hard disk, you would need to know the benchmark on the MB/s it can handle under random read/write tests.  Not what the drive controller is rated for, and not what the disk is advertised as, but what a real world test shows.

so that metric rsec/s is sectors.  typical PC drives can vary with the larger format so you'll want to check what your storage is.
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SandManAuthor Commented:
I got it guys, Thank you for your time explaining =)
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farzanjCommented:
Sorry, got too busy.  Could you kindly contribute your understanding on this thread.

Thanks.
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