[svlug] (forw) KVM vs Xen
rick at linuxmafia.com
Wed Oct 14 00:32:50 PDT 2015
Forwarded with permission from the main mailing list of Linux Users of
----- Forwarded message from Russell Coker <russell at coker.com.au> -----
Date: Wed, 14 Oct 2015 16:20:13 +1100
From: Russell Coker <russell at coker.com.au>
To: luv-main at luv.asn.au
Subject: KVM vs Xen
Xen has been widely regarded as the best performance VM for Linux for a long
time. Oracle has been one of the advocates of Xen claiming very close to
native hardware performance.
# 300% improvement in UnixBench score, with a KVM Linode vs a Xen Linode
# 28% faster at compiling a Linux kernel with a KVM Linode vs a Xen Linode
# Boot and shutdown times are greatly improved
Now Linode (one of the largest Xen sites) is moving to KVM, they list the
above as benefits of KVM which surprises me. My experience of Xen is that the
only way anything could be 300% faster is if it's an issue of disk IO
scheduling on hard drives (as multiple virtual machines on the same spinning
media causes contention and/or fragmentation issues depending on how you do
it. But given that Linode was already using SSD for all storage that's
obviously not what they are doing.
The last time I tried KVM on my laptop the performance was a lot slower than
native performance as opposed to Xen which was near enough to native hardware
performance that the difference didn't matter. I've never even tested KVM on a
server because the performance on my laptop (admittedly a couple of years ago)
was very disappointing. Last time I tested KVM performance was not only
noticably worse (EG compiles of selinux-policy-default taking about 50%
longer) but the increase in CPU use was an issue of cooling.
Has KVM improved a lot recently? How can anything be so much better than Xen
when Xen has been so close to native performance for so long?
I've just chosen KVM for a new Linode instance. They allow me to choose Xen
but say that KVM is the way of the future - presumably I would be forced to
use KVM sooner or later so it seemed easier to use it now.
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
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