[mythtv-users] Upgrade Suggestions - currently on myth 0.21 with PVR150, 250, 350

Raymond Wagner raymond at wagnerrp.com
Sun Jul 3 20:14:33 UTC 2011

On 7/3/2011 15:02, Richard Morton wrote:
>>> Unless you need to run multiple different operating systems
>>> simultaneously, or need to ensure complete isolation for testing or
>>> debugging purposes, it's best to avoid virtual machines and just run
>>> directly on the base system.
>> I don't agree with you here, but to each his own. My backend does not
>> run X, and except for needing direct access to tuners, I believe would
>> run quite well as a paravirtualized vm.
> I think Raymond is elluding to just that, the extra layer of
> complexity involved with vms having direct hardware access when they
> are in the sandbox. the vm layer would have to proxy calls and this
> potentially introduces a lot of code into the datapath.

What I'm referring to is really not related to trying to access hardware 
in a VM at all.  There are multiple different levels of isolation for 
the purposes of management are security, from a basic chroot (disk 
isolation), to jails, containers, and vservers (memory and network 
isolation).  Most tasks people use virtualization for do not need the 
overhead and complexity of full machine virtualization.  There are only 
a couple scenarios where you actually _need_ machine virtualization, 
rather than just get it as part of the package.

1. You are emulating a different architecture for compatibility or testing.
2. You are running a different kernel/OS for compatibility or testing.
3. You are making an image appear as a full dedicated machine for 
security purposes (honeypot).
4. You are doing HA services, and want to do live snapshotting, cloning, 
and migration of images from one physical machine to another. This is 
only relevant if the software in the VMs doesn't support such operation 
natively. Virtualization is the 'quick and dirty' route.

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