Linux aquaria 2.6.29-xen-r4 #18 SMP Sat Mar 6 17:39:44 CET 2010 i686 Intel(R) Atom(TM) CPU 330 @ 1.60GHz GenuineIntel GNU/Linu
aquaria ~ # hdparm -Tt /dev/xvdb

/dev/xvdb:
 Timing cached reads:   518 MB in  2.00 seconds = 258.45 MB/sec
 Timing buffered disk reads:  302 MB in  3.01 seconds = 100.44 MB/sec

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Linux aquaria 2.6.32-xen-r1 #1 SMP Sat Apr 10 17:23:45 CEST 2010 i686 Intel(R) Atom(TM) CPU 330 @ 1.60GHz GenuineIntel GNU/Linux

aquaria ~ # hdparm -Tt /dev/xvdb

/dev/xvdb:
 Timing cached reads:   424 MB in  2.00 seconds = 211.83 MB/sec
 Timing buffered disk reads:  140 MB in  3.02 seconds =  46.41 MB/se