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Old 11-19-2009, 05:57 PM   #1
kusanagiyang
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Registered: Nov 2009
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Smile Control / Manage hard drive


Hello,

Here is my general question about hard drive.

I need to slow down hard drive for my research project. With current, common hard drives, SATA I/II I/O do not ever saturate and become a threshhold in no condition, am I right?
If this is the case, the threshold is actually at the hard drive sequential/random x seek/read/write, again, am I correct?

After searching the net, I could not find a way to control / manage hard drive rpm, which, I thought, is a good way to lower/manage hard drive performance.

Could anyone give me any suggestion. Or, simply tell me that there is no tool to do it.

Thanks a million

Richard
 
Old 11-19-2009, 08:44 PM   #2
jhwilliams
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Well, hdparm will probably help you f* up your hard drive's throughput, if that's what your after. Set it to a low PIO mode, or something. I'm not sure I understand the point though: just hitting an I/O intensive read()/write() in for() loop in C will make your process io-bound and trash cpu performance, if this what you're after.

Also, you could just write a simple io buffer in C which refused to read more than so many bytes / second. This would simulate slower performance.

Code:
cat disk_file.txt | your_buffer_tool | whatever_you_want_to_see_have_poor_performance

Last edited by jhwilliams; 11-19-2009 at 08:47 PM.
 
Old 11-20-2009, 12:54 AM   #3
kusanagiyang
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Wink

Quote:
Originally Posted by jhwilliams View Post
Well, hdparm will probably help you f* up your hard drive's throughput, if that's what your after. Set it to a low PIO mode, or something. I'm not sure I understand the point though: just hitting an I/O intensive read()/write() in for() loop in C will make your process io-bound and trash cpu performance, if this what you're after.

hm... If CPU or memory bus is trashed, the hard drive activities are not actually overwhelming the hard drives, but its buffer, right? Interesting point, but this is not the effect I need.

Also, you could just write a simple io buffer in C which refused to read more than so many bytes / second. This would simulate slower performance.

hm... I don't know how to do this frankly... hehe
Also, come to think about it, how does linux kernel enforce this strictly?
The read ahead and hard drive buffer would become a new variable, which I have little control.

Code:
cat disk_file.txt | your_buffer_tool | whatever_you_want_to_see_have_poor_performance
Thanks for your suggestions. Appreciate it
 
  


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