Re: Performance hit of frequent smartctl -A listings

I've ran this command

% time smartctl -r ioctl -A /dev/sda |egrep "durat|real"
  info=0x0  duration=0 milliseconds  resid=0
  info=0x0  duration=10 milliseconds  resid=0
  info=0x0  duration=13 milliseconds  resid=0
  info=0x0  duration=150 milliseconds  resid=0
  info=0x0  duration=23 milliseconds  resid=0

real	0m0.236s
user	0m0.033s
sys	0m0.007s

and there's apparently an extra overhead besides the ioctl commands, which is expected but it's pretty cool to see a breakdown like this :)

This turns out to be a poor result on my system, though, as these numbers are two times less what they were initially on the first run:

real	0m0.421s
user	0m0.040s
sys	0m0.010s

Also, this data is for the older drive FUJITSU MHW2080BH.

My brand new WDC WD20NMVW-11AV3S0 external USB drives scored

real	0m0.067s
user	0m0.050s
sys	0m0.003s

and 

real	0m0.040s
user	0m0.033s
sys	0m0.003s

which is so much faster.

Ivan

On Dec 8, 2013, at 3:00 AM, John Gilmore <[email protected]> wrote:

>>> I was wondering if it is a good idea to have monitoring system call smartctl -A /dev/sdX somewhat frequently on my drives to monitor drives temperatures. I'm thinking 2-5 minutes interval, but I'm wondering how much of a performance hit on a drive is smartctl -A.
> 
> It probably varies on each drive; measure it and decide for yourself if
> it's impacting your performance.
> 
>>> In fact, I would love to monitor most of the values in in smartctl -A output, which could lead to about 17 calls each 5 minutes. I know this is a very dumb way to go about it, and some intermediary caching mechanism is perhaps a must, but still, how costly are these listings?
> 
> Don't "cache" it.  Call smartctl -A once and parse the listing once,
> to extract whatever 17 values you need.
> 
> 	John
> 
> 	


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