can a VM's harddisk be faster than the physical disk?
Stefan Sticht
sticht at sticht.com
Mon Jan 10 20:11:22 UTC 2011
Dear Ubuntu friends,
I have a little home-grown box whose VM's harddisk seems to be faster than the host's harddisk:
My Maverick VM:
root at keira:~# hdparm -t /dev/sda
/dev/sda:
Timing buffered disk reads: 1184 MB in 3.00 seconds = 394.25 MB/sec
root at keira:~# hdparm -t /dev/sda
/dev/sda:
Timing buffered disk reads: 1250 MB in 3.01 seconds = 414.66 MB/sec
root at keira:~# hdparm -t /dev/sda
/dev/sda:
Timing buffered disk reads: 1130 MB in 3.00 seconds = 376.05 MB/sec
My Maverick host:
root at black:~# hdparm -t /dev/vg0/vm
/dev/vg0/vm:
Timing buffered disk reads: 840 MB in 3.01 seconds = 279.41 MB/sec
root at black:~# hdparm -t /dev/vg0/vm
/dev/vg0/vm:
Timing buffered disk reads: 862 MB in 3.00 seconds = 287.06 MB/sec
The VM's disk is a qcow2 file on a LVM volume on a RAID-0 over 3 SATA disks. CPU is i7-920. Running Maverick with qemu-kvm 0.13.
Possible explanations? Is the time in my VM not accurate?
Regards,
Stefan
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