Dom0 is indeed faster in I/O operations than DomU. But if you are that
concerned about I/O performance, put the NFS server on a standalone
machine and not as a Dom0 which can compromise all DomUs running on it -
especially if it runs something like a NFS server.
The percentages vary, if you set it up correctly, a DomU NFS server will
be only ~10 percent slower than a native server.
Regards,
Daniel
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Marc Grimme
Sent: Wednesday, July 23, 2008 9:55 AM
To: Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list
Subject: Re: [rhelv5-list] guaranteed cpu power to VMs
On Monday 21 July 2008 16:52:32 Paul Krizak wrote:
> > One more question actually, this machine is gonna be a NFS "homes"
> > server for 30 Linux workstations. The homes are fairly IO busy, >
> especially when rsnapshot runs :) The question is, would such a >
> workload be happy to run in a Xen domU or should I be running it as >
> the dom0 ? I think it makes more sense to use it as the dom0!
>
> You should run the NFS server in a DomU. The Dom0 isn't "special" --
> don't confuse it with the Xen hypervisor, which runs *under* all of
> the domains, even Dom0. Dom0, for security purposes, should be locked
> down extremely tight. Any services that your box provides should be
> served by domU's, not Dom0. This is because anybody that can gain
> access to your Dom0 can manipulate your DomU's, which is a huge
security problem.
A little bit of topic but touches the specialty of Dom0 as well.
There might be reasons to put more functionality to Dom0.
For example performance reasons:
I've heard rumors that it is 20% faster to give blockdevices to DomUs
instead of directly using NFS/iSCSI or whatever IP based protocol
because the IP-Stack within DomUs is 20% slower then giving blockdevs up
to DomU.
Can anybody comment on this?
--
Gruss / Regards,
Marc Grimme
http://www.atix.de/ http://www.open-sharedroot.org/
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