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List Archive: gentoo-sparc
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To: gentoo-sparc@g.o
From: Zhang Weiwu <zhangweiwu@...>
Subject: O_DIRECT or buffered?
Date: Mon, 06 Dec 2004 09:55:38 +0800
Recently I did hdparm on my Ultra5 box with one standard hdd on-board 
(hde), one ATA66 hdd pluged on an IDE expansion card (hde). Result given 
below.

One question: why all of my other boxes (all my boxes using default 
value for hdds) shows "buffered cached read" speed, but this box 
"O_DIRECT cached read"?

I googled around and tracked some mailing list arguements, it seems 
O_DIRECT is just another mode than "buffered", which is very close in 
performance (said so by a hacker on year 2001), and I could just keep it 
as is. But I just put this question on the list in case I am wrong and 
could get knowledge from experts ^_^

sappho zhangweiwu # hdparm -tT /dev/hde /dev/hda

/dev/hde:
 Timing O_DIRECT cached reads:   576 MB in  2.00 seconds = 288.00 MB/sec
 Timing O_DIRECT disk reads:   66 MB in  3.04 seconds =  21.71 MB/sec

/dev/hda:
 Timing O_DIRECT cached reads:   576 MB in  2.00 seconds = 288.00 MB/sec
 Timing O_DIRECT disk reads:   20 MB in  3.30 seconds =   6.06 MB/sec




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Updated Jun 17, 2009

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