But if we run some risk analysis we will see that this is usually just fear and uncertainty and not a mathematically supported risk. If we assume the same risks as the example above then our single server will, on average, incur just a single total site outage, once per decade.
Compare this to the first example, which did the damage equivalent to two and a half total site outages – the risk of the virtualized, consolidated solution is only forty percent that of the traditional solution.
Now keep in mind that this is based on the assumption that losing someservices means a financial loss greater than the strict value of the service that was lost, which is almost always the case. Even if the service lost is no more than the loss of an individual service we are only at break even and need not worry.
In rare cases, impact from losing a single system can be less than its “slice of the pie,” normally because people are flexible and can work around the failed system – like if instant messaging fails and people simple switch to using email until instant messaging is restored. But these cases are rare and are normally isolated to a few systems out of many, with the majority of systems, say ERP, CRM and email, having disproportionally large impacts in the event of an outage.
So what we see here is that under normal circumstances moving ten services from ten servers to ten services on one server will generally lower our risk, not increase it – in direct contrast to the “eggs in a basket” theory. And this is purely from a hardware failure perspective. Consolidation offers several other important reliability factors, though, that can have a significant impact to our case study.
With consolidation we reduce the amount of hardware that needs to be monitored and managed by the IT department. Fewer servers means that more time and attention can be paid to those that remain. More attention means a better chance of catching issues early and more opportunity to keep parts on hand. Better monitoring and maintenance leads to better reliability.
Possibly the most important factor, however, with consolidation is that there is significant cost savings and this, if approached correctly, can provide opportunities for improved reliability. With the dramatic reduction in total cost for servers it can be tempting to continue to keep budgets tight and attempt to purely leverage the cost savings directly.
This is understandable and for some businesses may be the correct approach. But it is not the approach that I would recommend when struggling against the notion of eggs and baskets.
Instead by applying a more moderate approach – keeping significant cost savings but still spending more, relatively speaking, on a single server – you can acquire a higher end (read: more reliable) server, use better parts, have on-site spares, etc.
The cost savings of virtualization can often be turned directly into increased reliability, further shifting the equation in favor of the single server approach.
As I’ve noted before, one brick house is more likely to survive a wind storm than either one or two straw houses. Having more of something doesn’t necessarily make it the more reliable choice.
These benefits come purely from the consolidation aspect of virtualization and not from the virtualization itself. Virtualization provides extended risk mitigation features separately as well. System imaging and rapid restores, as well as restores to different hardware, are major advantages of most any virtualization platform. This can play an important role in a disaster recovery strategy.
Of course, all the concepts I’ve mentioned demonstrate that single box virtualization and consolidation can beat the legacy “one app to one server” approach and still save money – showing that the example of eggs and baskets is misleading and does not apply in this scenario. There should be little trepidation in moving from a traditional environment directly to a virtualized one based on these factors.