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Re: disk i/o performance problem



On Sat, Jun 02, 2007 at 10:54:51AM -0400, Douglas Allan Tutty wrote:
> On Thu, May 31, 2007 at 11:02:06PM -0400, WHIRLYCOTT wrote:
> > Etch: (output of hdparm)
> > 
> > 	/dev/sda:
> > 	Timing cached reads:   1588 MB in  2.00 seconds = 794.41 MB/sec
> > 	Timing buffered disk reads:  176 MB in  3.03 seconds =  58.15 MB/sec
>  
> > CentOS: (output of hdparm)
> > 
> > 	/dev/sda:
> > 	Timing cached reads:   4480 MB in  2.00 seconds = 2242.86 MB/sec
> > 	Timing buffered disk reads:  176 MB in  3.03 seconds =  58.16 MB/sec
> 
> The buffered disk reads are the same since that's the transfer rate from
> the drive's buffer.  The problem is the cache reads which is the time
> from you OS's cache.  
> 
I thought that the cached reads were from the disk drives onboard cache.

Regards,

-Roberto

-- 
Roberto C. Sánchez
http://people.connexer.com/~roberto
http://www.connexer.com

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