Michael Leone on 21 Jun 2008 16:22:54 -0700

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Re: [PLUG] Why Virtualize?

Matt Mossholder wrote:
> ----- "Casey Bralla" <MailList@NerdWorld.org> wrote:
>> But why not simply run dozens (hundreds?) of server **instances** on
>> the same 
>> server?   Why add the extra overhead of the virtualization process to
>> the 
>> hardware?   That has to cut efficiency by at least a few percent.
>> So what is the advantage of running a complete virtualized server
>> instead of 
>> multiple server processes?  I can think on only 1:  Clearly assignable
> I am in total agreement with you here. Consolidating applications to
> a
single server is a good thing. However, the factor that many people
forget to take into account is the additional cost savings that could be
had by consolidating software licensing as well. At my employer, someone
came up with the brilliant idea of using VMWare ESX to put a single
server at our smaller offices, to run all of the apps they use.
Unfortunately, these apps amount to:
>    * DHCP
>    * DNS
>    * File Server
>    * Print Server
>    * Site specific web server
> So, they decided to allocate a VM to each function. Of course, to remain within our company standards, each of these VMs also needed to run:
>    * BMC Patrol (problem monitoring)
>    * Anti-virus software
>    * Asset Management software
>    * Centralized remote access software
>    * Systems Management software
> All of these coses could have been reduced by 4/5ths if all of these
trivial applications were run on a single OS. None of them are
particularly complex, or likely to interfere with each other. That's not
even including the costs to purchase and maintain ESX and the price of
keeping all the additional OSs.

Well, splitting applications so that 1 server = 1 function, means that 
no application can bring down another function. For example, a tape 
backup should always be on a separate server, if you can. And use 
external devices. Why? If you should need to reboot to fix some SCSI bus 
errors, you're not taking out the file server, as well ...

DHCP and DNS should easily be on 1 server, or 1 VM instance, regardless 
of OS. File server and print server, also probably the same instance, 
and might even be the same instance as the others above. I'm a bit leery 
about putting high disk traffic applications (like file servers or 
database servers) on a VM.

The site specific web server ... maybe not. Depends on how much traffic 
this needs/generates, and the horse power requirements - will it take 
away from the others. We of course can't answer that, you can. But 
easily 2 VMs, instead of 5. And you can do 4 Windows servers on regular 
VMware (i.e., not ESX). I know, I used to do it. (I'm assuming Windows, 
since you mention anti-virus)

> Another advantage is political. It is often easier to get people to
> migrate to a VM (which can be done with tools) than to get them to
> reinstall their software on a new system, configure it, move the
> data, and point all the clients to the new system.
> Another advantage on the energy front comes from migrating running
> VMs between systems. VMWare calls it VMotion, Xen has Live Migration,
> etc.  I know with VMotion, you can do things like migrate a bunch of
> running VMs to a smaller number of servers at night, when load is
> low, and shutdown the excess systems, and then move them back out in
> the morning as load increases. >

You can do more, I've heard, and will learn, as I'm pretty sure we will 
be moving to take advantage of it later this year. ESX, with Vmotion and 
a good SAN, can make for a lot of interesting configurations.

Michael J. Leone                  Registered Linux user #201348

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