Whats the average lifespan of a server?
i'd really like to know what the lifespan of a server is, or could be. Is there something like lifespan in the world of PCs at all? Lets assume it runs 24/7, how many hours/days/years/etc could it be used?
Solution 1:
Do you mean before any part fails, at all? Or do you mean how long can a server be expected to last if you perform maintenance on the serve, including replacing faulty parts like hard drives and power supplies?
Assuming you mean the latter - after all components like a hard drive can fail any time from '2 days after you got them' to 10 years plus - then I'd say the lifespan of a server can be measured in two ways
You could consider its lifespan to be however long it remains able to do the tasks given to it, which might be some time if the task is something that never really changes, e.g. DNS server. This is common enough in businesses that don't give a lot of funding over to IT; I've always worked in "large business, big iron" environments, but this is a perfectly valid viewpoint in a small business, to some degree at least.
Or you could (and in my opinion, should) consider the lifespan to be for however long the hardware is supportable. In other words, once you can no longer obtain replacement parts for a server, it is essentially living on borrowed time. That doesn't mean you need to run out and buy a new server to replace an old one the very second you can no longer obtain parts to maintain it, but that at this point you have to balance the cost of replacing it against the cost/risk of not doing so and having the service it provides unavailable until you can purchase a new server and migrate the old server's apps and data over to the new one.
In addition to both/either of the above points, you might also consider the point at which an old server becomes inefficient to maintain - the cost of keeping it running becomes greater (maintenance, power, floorspace in some cases) than the cost of virtualising it and a bunch of other similar older servers on new hardware.
EDIT: I think it depends too on the task that server is doing - there's a big difference between a DNS server, say, and a database server running a major CRM backend that the business is paralysed without. Both in terms of risk to the business if it dies unexpectedly and in the efficiency gained by moving to newer hardware.
Of course you could migrate the CRM backend to new hardware and re-purpose the old hardware. We've done this a few times for non-vital test or dev environments, etc.
Solution 2:
Most people have so far answered this with a view to the technical life span of a server. Which is pretty much what most small companies and private owners do. I work for a company where there are no cash flow problems, and our approach is quite different.
Our servers (and most other pieces of IT infrastructure) are all assets, i.e. they are capitalized and as such they get written off over a number of years. For most items, this happens over a period of 4 years. After that, these items have an asset value of 0. In other words, they are not assets any longer. And if they are not assets, they become liabilities.
Therefore we swap them out for new ones, and the old ones get donated to charities or other worthy projects (e.g. some of them go to the Debian project, if they are interested). From a financial viewpoint, purchasing an asset simply swaps money for a different kind of asset. From an IT perspective I can rely on the fact that all my kit is covered by warranties, that spares are available and downtime is minimized.
At the moment our oldest server is 6 years old, and the replacement for it is already on our configuration bench.