For sure working in a datacenter has its advantages.
One of them is the lifecyle of production servers, and what you can do once they are dismissed from production. In the past months we dismissed some HP Proliant DL380 G5. Quite old for our computing needs because of the CPUs they can use, too much power-consuming compared to the G7 we are using and the new upcoming G8 we will for sure add in the upcoming months. 
They were headed to the dumping ground probably, so why not try to use it for a lab? We were looking for a new revamped lab in our datacenter to create a small vCloud environment and try out all the new stuff and test configuration changes before doing them in production, so I killed two birds with one shot by offering myself for the new lab creation, and thus becoming its owner (well, I used “manager” during the meetings about it, you know…)
Why: I already talked about different lab configurations in a previous post, and as I wrote there “If you’re lucky enough to have large rooms, low electricity costs, and a good budget, this (the Full Lab) is obviously the perfect solution”. Among the cons, I listed expenses, electricity bills, space and noise. All these problems become less important if you place this kind of hardware in a datacenter: 4 servers out of hundreds have small impact on electricity bills, so as to space and noise. And about expenses, those servers were bought 4-5 years ago, so they already paid for themselves by running VMs for years.
What: Long story short, I now have a new shiny lab that really overpowers my home vlab: 3 HP Proliant DL380 G5 servers, each with two E5345 Quad Core CPUs and 20 GB ram. I know some of my customers have less power in their own production clusters… 
A 4th server has “only” 14 Gb of ram, so I decided this is going to be my storage server. I installed ESXi 5.1 even here, and I filled the 8 slot disk cage with 146 Gb 10k SAS disks refurbished from other dismissed servers. Using the embedded P400 raid card, I created a 900 Gb raid5 disk. On top of it I will install some VSA to have my iscsi storage. How: thanks to the network infrastructure we have, I now have separated VLANs for management, lan, vmotion, FT and iscsi. Using the 4 nics, I grouped them in two distributed vswitches with multiple paths, like this:
On top of all, ESXi 5.1 and vCenter 5.1, with separated VMs for vCenter, SSO, Active Directory Domain Controller, and a SQL 2008 R2 dedicated VM. And many more to come.
What I’m missing: a better and faster storage. The actual storage is acceptable, but is clearly a big bottleneck for my lab for both performances and space. I will see in the future what I will be able to add to it. If any storage vendor is out there reading, and want to put a cute banner on my website and help me, all you need to do is give me an iscsi storage 🙂
The future: playing with it, breaking it, rebuilding it, learning new stuff 🙂