Dne, 30. 01. 2011 21:15:49 je T o n g napisal(a):
Hi,
Talking about VM, some prefer virtulbox, some VMWare. Don't know how
many
of you prefer kvm. I'm wondering if you could do the speed benchmark
of
your preferred VM, and compare the result to that of your host.
The reason that I'm asking -- recently I noticed that my kvm is
extremely
slow, its disk access seems at least 10 times slower (*12 hours* to
restore a 600M partition?!). Googling revealed that's a known problem.
e.g.,
http://blog.kagesenshi.org/2008/03/qemu-slow-disk-throughput.html
"... I uses Qemu for hosting the guest OS for my development
environment.
For 2 days, I keep wondering why Zope/Plone loads damn slow on the
qemu
machine eventhough I have allocated both cores of the processor, and
512RAM for it. 15 minutes simply to start up is really not desirable.
I
kept on investigating and guess what:
[root@unapcict ~]# /sbin/hdparm -t /dev/hda
/dev/hda:
Timing buffered disk reads: 18 MB in 3.03 seconds = 5.95 MB/sec
Just for a comparison, the host hdd's speed:
[root@Nobuyuki ~]# /sbin/hdparm -t /dev/sdc
/dev/sdc:
Timing buffered disk reads: 174 MB in 3.01 seconds = 57.71 MB/sec
Darn.. So, thats what the reason. . . "
See, it *IS* at least 10 times slower.
Please comment.
a) In the most general user case scenario, kvm uses a *file* as a
virtual disk. A file can get way more fragmented than a disk would, and
incurs major overhead even when it's not fragmented.
b) You sure kvm is *actually used*, and not the non-accelerated qemu?
--
Cheerio,
Klistvud
http://bufferoverflow.tiddlyspot.com
Certifiable Loonix User #481801 Please reply to the list, not to
me.
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