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11 golden rules for virtualisation

Posted on 5 Aug 2010 at 16:34

8) Lie about the money

Free virtualisation software can achieve amazing things. Perhaps the most amazing is to drive your board completely round the bend – the way basic hypervisor code is often given away for nothing, and then one or another utility turns out to cost £5,000, is the cause of immense angst inside projects.

The virtualisation vendors think of this “upsell” as a good thing. The reality is, it’s an Appraisal Meltdown Device. So rule eight says: do not admit when you’re about to use a free tool.

Keep the freeness to yourself, for your prototyping period; cost the whole approach based on getting all the bits you want, as a lifecycle view, even in the initial project-scoping conversations.

9) Watch the big guys

So much of what’s offered in the virtualisation marketplace is there to turn this architecture into a must-have purchase decision for large corporates.

So we see tonnes of effort directed at producing mobile guests – not VMs on your phone, guest machines that can move from one host to another without anyone using them realising it’s happened.

This is how we come to have snapshot-based backup (so each backup takes only a few seconds) and central management tools that quote collections of guests up into the many hundreds, all visible from one software interface: tools that don’t really kick in until you have a truly large network.

There tends to be an incredulity gap between large and small LAN deployments – the big boys can’t understand how small networks get by without massive management toolkits, and the small players can’t work out how on earth the big guys spend so much money. To make good use of a virtualisation tool, you have to put some time into understanding the world it’s most commonly sold into.

10) Upgrade the other bits

You may well find your NAS is too slow to get through a VM backup in time, or you need to spend money on a Layer 3 switch and someone to set up the IP config for you in a usable way.

So, in the course of that virtualisation project you end up blowing £10K on a chunky Cisco switch, a few iSCSI disks and a couple of external storage arrays.

Notice we’ve slipped in another frequently encountered hurdle by referring to extra storage arrays in a server. If you’re used to a single channel of SCSI with lots of gigabytes hanging off it then prepare for a multiserver virtualisation project to expose the performance shortfall of that architecture. Virtual machines love disk I/O.

This is equally true for smaller businesses. Once you start looking at making a server with six or eight separate storage devices, each one at least mirrored or showing some other type of fault tolerance, the costs soon crank up even based on eSATA controllers and drives.

11) Don’t virtualise file servers

File servers do one simple low-processor task with lots of disk capacity, but the best servers to virtualise need little disk space while performing lots of complex jobs.

Most often when the term “virtualisation” is used referring to file servers, the speaker is talking about having file servers hosted, not “virtualised”.

Big players may say they’ve broken out of this “don’t” and “it’s all virtual” – they’re using a SAN as a giant pool of disks and their version of a “file server” just brokers file requests between PC LAN on one side, and SAN HBA connections on the other.

Author: Steve Cassidy