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John_Gill
12-Jul-2012, 11:45
Hi,


Running SLES11sp1 with Xen virtulization.

I want to run DNS/DHCP on the host server and also run a mixture of Windows
and OES VM's using XEN. The VM's are all low utilization.

I guess this is possible but perhaps the best solution is not to run any
software on the host, but rather create another VM for the DNS/DHCP.

Any ideas or thoughts ....
Regards
John

ab
12-Jul-2012, 14:18
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I am often tempted in this same way; the host has enough power, the
application has low requirements anyway.... what's a person to do?

My current (though subject to change pending new information, of course)
opinion is that a VM host should do as little as possible outside of
managing VMs. Even though DHCP and DNS are typically no-utilization
services (for the majority of environments) they are also critical and
that, to me, makes them ideal for virtualization. Something goes wrong?
Move the VM elsewhere rather than setting up something new on another
machine at the last minute. The VM(s) created to handle these services
can be really, really small and with minimal resources since all it
needs to do is boot and run a couple of services (sshd, bind, dhcpd) and
you're done. Migrating from one box to another with this small of a VM
is then pretty trivial, even to an already-busy box since this won't add
much to it (though these services still need to have their place so
don't put them on a laggard).

The container technology available in SLES 11 makes me excited for these
very kinds of services. Having a "container" (vs. a VM) that is
dedicated to something like DNS and DHCP (or one for each perhaps) that
can be easily moved around without the 512 MB RAM and hardware emulation
involved in creating a VM is really appealing.

Good luck.
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John_Gill
12-Jul-2012, 15:15
Thanks AB,

You confirmed my thoughts on Hosts and VM's.

John