Virtualisation is clearly one of IT’s great fashions, and as such continues to attract huge amounts of interest. Unlike many technology-based fashions - and we can all remember quite a few - virtualisation solutions are being deployed in anger in many areas, especially in the world of x86 servers. As is well appreciated, getting …
The case for virtualisation?
I’ve tried to understand why I would want it. Most applications I run require 100% of the server resources so sticking 20vm's on one server doesn’t get you 20 servers, it gets you 20 slower servers with an overhead for the VM-OS.
The one situation I can see it being useful is large scale distributed servers for processing information. Such as large websites. Where one can have a single copy of a virtual OS, with the sites source code replicated onto all the servers. Need to update all your servers? No problem, update the original VM image and reload the OS's sequentially. That only works if you have a propperly connected SAN + database system.
The other application is legacy software that only runs on nt4....
Has anybody any other insights into why they use VM's?
Many of the apps I use can only use a single CPU. They will pin a single core, but are worthless beyond that. Combined with the numerous smaller VMs (for example, a domain controller, or a WSUS server,) that simply don't eat any real resources. These types of servers make perfect sense to virtualises, and we have en masse.
Cheap 2 socket servers come with 8 or even 12 cores now. That application that can only use a single core makes that kind of server a total waste.
Why use virtualisation? Because programming techniques have not adapted to a multi-core world. Oh, and the ease of management, ability to move my VM from one piece of iron to the other in seconds, ease of cloning, etc. etc. etc.
Standard reasons, really.
> Has anybody any other insights into why they use VM's?
Because it means buying more expensive servers, of course.
Given that a pretty decent server can be had for sub £1000, this means IT deps are no longer in charge of big, expensive boxes.
Want a machine capable of multi-Gbs of RAM and disk, and many CPUs? That'll be right at the top end of the market then - so IT departments are happy they're 'important' once more.
This leads such hilarity as the VM for the 1-month of training in an org being charged to the project at an amount twice the cost of the *entire* live server !