[mythtv-users] Back-end Virtualization

[Nathan Hawkins]

On 5/11/2012 14:34, Nathan Hawkins wrote:
> @Ray - you mention several  good reasons why virtualization isn't 
> desirable, and I agree that for the majority of people its not the way 
> to go because they simply don't have the raw computing needs that some 
> others do. In my case its ALL about efficiency... Strictly from a 
> power perspective (which translates to TCO), it costs less to 
> virtualize. I, however, demand my hardware to actually/continually 
> work rather than sitting idle 99.9% of the time. Virtualization allows 
> me to get far more efficiency for the same hardware, thus TCO goes 
> down while pushing my gear to do the same amount of work on less 
> hardware and power.

You're missing the whole point I've been trying to make.  Virtualization doesn't do any of that.  Reduced redundant hardware needs, improved hardware utilization, it comes from just moving multiple applications onto a single piece of hardware.  In a commercial setting, virtualization merely allows you to do that while retaining the old security levels you got from having physically independent systems.
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No... I got your point. Security plays a very little role in what I'm trying to do, and Virtualization does everything I said it does... I'm not talking theory. I'm talking from practical experience. Regardless of what your opinion is or perhaps your experience. I am talking directly from what I have going on at this very moment. I'm not sure my hardware resources could be used more efficiently then how they are working.

> They all have their function, but you simply cannot have one huge 
> beefy master server doing it all... I've tried it and it simply 
> doesn't work. If you take that same beefy server and dice it up into 
> VM's...you get soooo much more out of that hardware.

That makes no sense what so ever.  A single Linux server is not sufficient to run multiple independent applications, but take that same hardware, run all the same applications, but now each with its own kernel performing redundant duties, and wrap them all in a hypervisor running many of those same scheduling, memory, and IO management tasks, and somehow it all runs better?  Something doesn't add up there.
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Again, it doesn't have to make sense to you. Frequently in the IT world things "appear" to not make sense until you get to the actual reasons how and why OS's and applications work the way they do, but let me assure you that you cannot take every application under the sun and run it on its own Daemon on a very robust system and have it run more efficiently then dividing those applications up into VM's. It's the way applications and hardware architecture works out... Sometimes you have to just do it, rather than talk about it. The results are frequently quite different then what was originally theorized...

> So, the real question is why NOT virtualize? These days,  computers 
> are becoming so much more necessary in day to day life that I find it 
> increasingly necessary to become increasingly more efficient.

And that's what I've been trying to explain.  Virtual machines get you some high availability features, if you're willing to pay a whole lot for your solution, and which have little to no benefit for MythTV users.

Virtual machines get you nearly all the same level of security that independent physical servers used to, but when MythTV doesn't even attempt to restrict access to be called "insecure", use to that end is a bit misguided.

Virtual machines allow you to run different system architectures and different operating systems, such as a Linux mythbackend and a Windows domain controller.  That one is a bit more difficult to argue against for a home user, but using Samba, running a second physical server, or running a virtual machine on top of a Linux host rather than a shared hypervisor would all be potential alternatives.

Virtual machines allow you to test things that could potentially crash your operating system without affecting other tasks running on the same hardware, but that's something that would be more common for development or testing purposes, rather than something you would expect to experience on a production system.

The real, key feature everyone seems to gung ho about in regards to virtual machines is the ability to run isolated Linux installs, where changes to shared libraries for one application will not screw up another application.  This can be done just as well without running a virtual machine, and when MythTV needs hardware access that causes all sorts of problems with trying to use virtual machines, it seems the sensible solution is to simply not do so.
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My only response to this is "perhaps". Every situation is different, and again, practically speaking you can theorize all you want. When you put it into production, it frequently doesn't work out the way you thought. There are reasons for it, but a lot of the time a VM solves the issue...and I'm ALL about efficiency...

> Combine that with I really like Hauppauge and the answer is this  USB 
> 64 bit 950 (now the 950Q).

Actually, the 950 and 950Q are two very different devices, despite the similarity in their name.  The 950 is an ATSC (broadcast-only) tuner, while the 950Q is capable of QAM, or unencrypted digital cable.
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I wasn't aware of what the differences are, but its not real relevant to getting Myth to work in a VM. I do appreciate the clarification!