[mythtv-users] Multiple backends

Christian Szpilfogel chriszpml at gmail.com
Fri Mar 25 23:29:23 UTC 2011


On 20/03/2011 4:03 PM, Raymond Wagner wrote:
> On 3/20/2011 11:50, Raymond Wagner wrote:
>> On 3/20/2011 11:50, Raymond Wagner wrote:
>>> Last, don't use a VM.  There is very little reason for any home user to
>>> need to use them.
>> On that I disagree. YMMV, but it allows segregation of functions
>> which makes admin a lot easier. On my server I have three different
>> incarnations of Debian running. For some stuff I need an up to date
>> version - so it's got Squeeze. For other stuff, it's too much hassle
>> at the moment to upgrade everything, and that's still running Sarge.
>> And then I've got stuff in between running Lenny.
> On that I disagree.  You would be just as well off running another
> install in a chroot.  All the same file and library isolation as a
> virtual machine, with none of the overhead.  If you need network
> isolation, well then there are security containers that can handle that
> without the overhead of full virtualization.
>
> A home user wouldn't care about any of the HA and live migration
> capabilities of enterprise VM software, so the only remaining thing it
> would offer is the ability to run multiple kernels and system
> architectures simultaneously.  Considering no VM is going to provide
> much meaningful hardware access, there's no need to run multiple
> kernels.  That same userspace which runs on a 2.6.18 RHEL5 kernel would
> run just as well on a modern 2.6.38 kernel in a chroot.
>
I have to agree with Simon. While chroot is fine for some, using some 
form of virtualization adds the following benefits:
* run different kernels and migrate each kernel only as you need to
* Using the above run different distros and pre-packaged virtual apps as 
you need them
* quickly and easily make snapshots of current guests and simple 
restores (Simon gave an example when fiddling)
* Migrate entire guests to new platforms as necessary
* Quickly create a guest and quickly destroy it as needed.

I will agree that using virtualization is best with multi-core 
uProcessors. I use an Intel Core 2 Quad. I am currently using VMWare 
Server 2 (have been for years) and am now planning to move to vSphere 4 
to gain the advantages of bare metal virtualization. There are other 
options of course.

Using a Virtual Machine has given me much flexibility and saved me a 
tonne of effort over the years including effectively risk free upgrades 
with mythtv.

However it is not perfect. For effective use you should install the 
vmtools into the guest. Some I/O interfaces are not available (e.g. 
firewire). On some hypervisors PCI/PCIe cards are not practically 
accessible.



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