Oh, yeah... iostat. Forgot about that.

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Ever have your software raid go from ZX-81 fast mode to slow mode?
Try this:
iostat -x 1 3

Throw in -d for just disk
iostat -d -x 1 3

Watch parity writes with this:
iostat -xmd 1

I should parse and graph that per device.  Would give an easy way to spot the drive on the outs.


This is nice too (to see per process io):

pidstat -d (disk io)
pidstat -r (memory)


I found that 1 disk was consistently slow in an 8 disk software raid 6.
Since it was software raid, I just kicked the drive out to prove the point!
Throughput doubled after kicking the troublemaker out!


This is good for gathering other info:
atop
It logs so you can check up on things later on a per process basis.
when running interactive mode try this:
v (verbose process info)
d (disk)
m (memory)
c (running command process info)
p (process totals)
u (user totals)
n (network totals) - needs patches on old kernels
f (show / hide inactive procs)
g (generic output - default)
^F - forward 1 page, ^B - back a page, ^L redraw the screen.




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