[mythtv-users] Back-end Virtualization

Raymond Wagner raymond at wagnerrp.com
Fri May 11 17:37:08 UTC 2012

On 5/11/2012 13:19, Zarthan South wrote:
> On Fri, May 11, 2012 at 10:51 AM, Raymond Wagner <raymond at wagnerrp.com
> <mailto:raymond at wagnerrp.com>> wrote:
>> On 5/9/2012 21:22, Nathan Hawkins wrote:
>>> Is ‘Anyone’ virtualizing their backend?! I cant believe I’m the only
>>> person out there who wants to do this…
>> Why do you want to want to virtualize your backend? "Because I think
>> it would be interesting" is a perfectly valid reason here.  "Because
>> the industry uses it and VM vendors tell me it magically makes
>> everything better" is not.  So why does industry use it?
> The first reason is to more fully use physical resources. 90 plus
> percent of physical machines use less than 10% of the CPU.

No.  Contrary to popular belief, modern operating systems are actually 
capable of multitasking without the help of virtual machines.

> Up until recently security and the inability to ensure network traffic
> security was very much lacking. Today unless you spend the extra money
> for all the security measures you do not have any means of protecting or
> monitoring inter VM traffic.

And this gets right back to the third paragraph, if you think you need 
the level of isolation virtualization provides for the purposes of 
security, either you're an absurdly paranoid home user, or you need to 
seriously reconsider whether MythTV is a good fit for your commercial use.

>> The second reason is high availability.  The virtual machine allows
>> you to save the state of the machine, and in the event of a failure,
>> resume that state on another piece of hardware.  This is really only
>> a crude route to high availability, as such capability is much more
>> effectively and efficiently performed by the application itself,
>> such as MySQL clustering and replication servers.  It becomes a
>> question of how valuable is the application to your needs, and is it
>> valuable enough to warrant the time and expense developing native
>> support in the application.
> Reduced datacenter space and power and cooling. A dual multicore CPU
> server can easily handle a 20 to one ratio and virtual desktops can go
> 100 to one.

As stated, you actually can run multiple programs on a single operating 
system these days.  All that preemptive multitasking developed in the 
1970s is wonderful stuff.

> During off peak hours I can migrate VM to fewer physical servers and
> shut down the extras. When needs change I can run up the extra physical
> machines and migrate the VMs back.

This comes back to high availability, and application clustering.  If 
you need the ability to migrate a live instance of an application from 
one physical machine to another, virtual machines are just about the 
only easy route.  If instead you are running something like a web server 
that has no trouble handling a restart, there is no reason you cannot 
simply terminate the instance on the machine you want to power down, 
open a new instance on the machine you're migrating to, and update your 
load balancers to suit.  Virtual machines would not be necessary.

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