> From: Edward Ned Harvey
> [mailto:opensolarisisdeadlongliveopensola...@nedharvey.com]
>
> In order to test random reads, you have to configure iozone to use a data set
> which is much larger than physical ram. Since iozone will write a big file
> and
> then immediately afterward, start reading it ... It means that whole file
> will
> be in cache unless that whole file is much larger than physical ram. You'll
> get
> false read results which are unnaturally high.
>
> For this reason, when I'm using an iozone benchmark, I remove as much ram
> from the system as possible.
Sorry. There's a better way. This is straight from the mouth of Don Capps,
author of iozone:
If you use the -w option, then the test file will be left behind.
Then reboot, or umount and mount…
If you then use the read test, without the write test and again use
-w,
then you will achieve what you are describing.
Example:
iozone -i 0 -w -r $recsize -s $filesize
Umount, then remount
iozone -i 1 -w -r $recsize -s $filesize
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