[ale] Virtualization

[Jeremy T. Bouse]

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	Like with anything there are right and wrong situations for using it.
If you have a very high I/O application, then pushing it into a
virtualized environment is going to be error prone. I've worked with
both VMWare and Xen, actually worked to help put together the Xen
packaging team for Debian. Now RHEL5 include Xen as their choice of
virtualization.

	I've been making use of a dual quad-core server with ample amounts of
RAM using Xen to actually improve the performance of a monitoring
platform. Running without virtualization the system was actually bored
but yet not performing as efficiently as it should have given the
server's resources. Rebuilt using Xen and putting my monitoring pollers
into VMs I got serious performance gains by splitting the load and
finally got the server to fully utilize it's resources.

	That said I have instances where I wouldn't consider virtualization as
it the application would put too much demand on a single VM which if not
properly configured could starve Peter to serve Paul.

	If you've got the environment with use of a SAN and multiple host
servers for VMs you can add good HA to the mix as any of the hosts could
fire up the VM which utilize the SAN for their data rather than local
HDD resources.

	As someone mentioned earlier if it's poorly thought out and implemented
it will be begging for an epic fail. It is all in how it's designed and
implemented.

Jeff Hubbs wrote:
> My experience - by which I mean VMware ESX in two workplaces and Xen on 
> my own - is that virtualization is a case of making deals with the Devil. 
> 
> Hardcore this-is-what-I-run-production-on ESX use calls for exquisite 
> levels of care, feeding, money, and intelligent thought.  If your IT 
> organization doesn't have enough of any of these elements to expend on 
> your ESX plant, epic FAIL awaits.  Everything at every level must work 
> well and perfectly, for they will be stressed and anything that's not up 
> to the task will have everything on and above it crashing down. 
> 
> VMware did a reasonable thing by making ESX something that you install 
> on bare metal, but in exchange you lose interoperability and 
> flexibility.  I liked dealing with Xen (at least as it existed in 
> mid-'07) because it insinuated itself at a fairly low level - your host 
> instance can be truly yours - and I am drawn to the idea of using 
> virtualization for R&D purposes, i.e., that's where server instances 
> "gestate" before going to real hardware for testing and then production. 
> 
> I am also seeing virtualization as a legitimate way of addressing 
> spiraling electrical power consumption.   It makes me feel as though 
> using virtualization to *some* degree could be reasonably considered to 
> be a requirement for responsible computing. 
> 
> Disk subsystems seem to be an Achilles' heel of VM rigs...the next time 
> I try anything like this, I want to try basing it on ATA-over-Ethernet.  
> The high-dollar canned (rhymes with "crap") iSCSI subsystem in use at a 
> former workplace of mine was way too accident-prone to depend on. 
> 
> - Jeff
> 
> 
> 
> 
> 
> Jim Kinney wrote:
>> On Tue, Feb 24, 2009 at 9:50 PM, Christopher Fowler
>> <cfowler at outpostsentinel.com> wrote:
>>
>>   
>>> This is my experience as well.  I think many companies look at
>>> virtualization as a way to save
>>> money on hardware.
>>>     
>> Virtualization seems like a cool toy. But when I see a business use
>> many virtualized machines for daily processes, mission critical
>> services, etc, it just screams "single point of failure with massive
>> consequences".
>>
>> It also speaks volumes about the overall architecture and design of
>> the processes in use that they require multiple machines for load that
>> then get virtualized to save money on hardware.
>>
>> ?!?!?!?!?
>>
>> Huh?!? WHA?!?!?
>>
>> Picture this scenario: Product FOO is composed of database, app logic,
>> and UI frontend. The designers all insist that their portion requires
>> an independent machine to avoid resource conflicts. So 3 VMs get built
>> thus placing all the parts on the same machine with even higher
>> overhead than if they were on a single, physical machine. Management
>> viewpoint is they don't have a new chunk of hardware to buy for this
>> process. While true, they did have to buy a HONKIN' box(s) for the vm
>> server.
>>
>> It always seemed to me that virtualization is a good thing for test
>> environments and extremely light loads that are not mission critical.
>> But the ideal use in a mission critical environment is as a backup
>> environment for the real hardware.
>>   
> 
> 
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