In the second comment around the right time for datacenter refresh, I'd like to look at Costs. Power is covered in the comment from Chris and I covered some comments on Space already in the discussion forum. So what it really boils down to is cost of running your existing datacenter versus the costs of throwing the servers out and replacing them. It is clear also from the other comments, that it doesn't make sense to throw out servers which are utilized in average 15% and have them replaced by new servers, which are 5 times faster and utilize the servers 3%... Great achievement hu?... Server Refresh makes therefore most sense to do only when consolidating the environment. How do I consolidate the environment? By using virtualization. See Helmuts blog and the whole theme next week on that topic.
Therefore let's look at the real cost factors, when refreshing the servers:
Cost of new hardware: That is obviously a significant capital expenditure and starting at about 2000$ for a reasonable DP server. But the trick is also that a lot of server companies offer financing models which make this an operational expenditure. But key is also to understand, that by consolidating your servers at the same time the depreciation costs of the servers may actually decrease, as you have less hardware to depreciate!
Maintenance costs: Again, reducing the number of servers running given applications, and at the same time unifying the environment helps significantly to reduce the maintenance costs. This can be a significant step in unifying on a given OS or hardware platform.
Power consumption: Similar to utilization, it doesn't make sense to just look at the power consumption by server, but at the consumption by performance and therefore I can save about 38% in power bills, on a given workload vs. the previous generation hardware and about a 10th of the power of hardware which is 2-3years old. Again, obviously only, if I do this in combination of consolidating the servers. Trick often is, that those costs are often not taken into consideration, as those are not billed to the IT department but to the facilities group. So it becomes an executive decision to ensure they are looked at!.
Switching costs. Obviously very hard to measure, as this depends on the environment of the customer. And I talked to the customer who said: "No I will never touch this AS400 system, as it just runs and runs and runs." On the other hand I had a customer who replaced just those AS400 systems and saw huge synergistic effects, because he put the application on a standard based architecture and was able to finally integrate it in the other production system and therefore have one reporting and analytics tool.
I try to make a long story short. This is not something you do very often, but you don't get married every year either. But most of the time it's worth going through the efforts. So thinking about replacing the servers which are older than 2-3years is definitely worth while and often an effort which pays off in the first year!