Jürgen Keil wrote:
Dom0

amber ~ # uname -a
SunOS amber 5.11 snv_113 i86pc i386 i86xpv

amber ~ # /usr/gnu/bin/dd if=/dev/zero of=/tank/test count=100000
51200000 bytes (51 MB) copied, 2.70782 s, 18.9 MB/s

DomU :

corwin bruno # uname -a Linux corwin 2.6.18-xen-r12 #7 SMP Fri May 8 10:41:05 CEST 2009 x86_64 Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz GenuineIntel GNU/Linux

corwin bruno # dd if=/dev/zero of=/home/bruno/test count=100000
51200000 bytes (51 MB) copied, 0.504987 s, 101 MB/s

Now that is a 1 to 5 performance gap !!
Any ideas about how to explain this ?

Are you sure that linux has actually written the data to disk
when the dd has returned?  In most cases (esp with such
a small amount of data) linux has the data in it's buffer
cache and *not* on the disk.
Well, that could be an explanation... I can test with more data to see if there is any difference...

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