As I discussed last week, the benefits of virtualisation are

many: lower physical space requirements, reduced hardware costs, reduced power

consumption and cooling, and the ability to rapidly deploy new services. There

are, however, some increased risks which come with virtualisation. Let’s take a

look at what they are and whether there are ways of neutralising them without

losing the benefits gained.

The stability of our virtual systems will, of course, rely

on the host operating system. If the host system crashes or is taken down by

some other problem (a virus, perhaps), then all of our guest systems on that

host will be taken down. This ties into an obvious risk behind migrating many

servers and services onto one physical platform—that a single hardware failure

will affect multiple virtual systems, putting all of our eggs in one basket, as

it were.

Thankfully, some of the benefits of virtualisation can help

us overcome this risk and increase the resilience of our systems overall. How? First

of all, the nature of virtualisation means that backup procedures can be

greatly simplified; snapshots of complete virtual machines can be taken periodically

for very fast recovery. For those using hardware virtualisation, there is the

additional benefit of hardware isolation, meaning that recovery no longer needs

to be made to a host with an identical hardware configuration. In my opinion,

the greatest gain conceived by virtualising services and systems is the most

comprehensive safeguard against hardware failure—the increased affordability of

high availability computing. Sure, by consolidating four servers on to one

physical platform we have made substantial savings; however, we could choose to

set up a high availability cluster. Consolidating four servers into two will

still produce substantial savings and with increased redundancy over the single

server-single service model; we are not only negating the increased overall

risk posed by hardware failure, we are making very real gains as high availability

redundancy is created.

One risk posed to smaller companies is not directly caused

by potential vulnerabilities or bugs. In an effort to maximise savings

(possibly egged on by the availability of free server virtualisation software),

the risk is that projects may be pushed forward into production without the

necessary investment in staff training or consultancy. This can result in

inadequate capacity planning, incomplete configuration of both the host and

guest operating systems, and a poor understanding of the administrative

requirements to keep things running smoothly after deployment. These

misjudgements could lead to poor performance and possible system failures. In a

production environment, this can result in spiralling costs through either loss

of revenue or consultant’s fees (to fix the mess). It’s therefore necessary to

make sure that the planning phase of any virtualisation project is

comprehensive and not fleeting; staff training should also be considered as an

essential component and unavoidable cost.

As you can see, there are very real risks which need to be

taken into account when deciding whether virtualisation is the right choice for

your organisation. I personally believe that with the use of high-availability

computing and snapshot-backups, these risks are negated. Rather than it being

the case that virtualisation is increasing our vulnerability to hardware and

system failures, it is actually increasing

resilience while still saving resources. A very interesting reference on the

topic of high availability configuration of virtualised systems can be found here.

Have you recently undertaken a virtualisation project? What problems

have you come across? How did you overcome them? If you are still considering

making a move, what potential issues are holding you back?