6. Use an Existing-Infrastructure Profiling Tool
Virtualization vendors offer several tools that can forecast what hardware you’ll need to move a physical infrastructure into the virtual realm. These tools, such as VMware’s Capacity Planner, require some setup and configuration, but can provide a wealth of extremely useful information before you spend a dime on production hardware.
These tools employ constant performance profiling to gauge the resources that each server on your network consumes, generally over a period of time from 30 to 60 days. They see the peak utilization of CPU, RAM, disk, and network I/O resources, and mix all of that data together to produce a guide to the CPU, RAM, storage, and network requirements you’ll need to shift the infrastructure into the virtual world. In some cases you can even define the brand and model of the servers you’re considering, and the tool will tell you how many you need. Playing with the numbers here can save you plenty of money down the road.
7. Spec and Purchase the Production Hardware
Based on the results from your lab testing and capacity planning, you should have a good idea as to what resources each of your physical host servers will require in production--at least to a point.
Spec out the servers to be identical units, from the CPU model to the amount of RAM present. In some instances it’s much more financially sound to add another server than to add high RAM counts in a smaller number of servers: Since higher-density RAM is notably more costly than lower-density RAM, you may find that it’s cheaper to purchase, for example, six servers with 32GB RAM each than three servers with 64GB RAM each. Buying a larger number of servers has the added benefit of broadening reliability, as you'll have more physical servers to take the load should a failure occur.
As far as storage goes, you’ll get more bang for your buck with iSCSI or NFS storage than with Fibre-Channel at this point, especially in lower-scale projects. Regardless, make sure that your storage vendor is approved for use with the virtualization software you’ve chosen, and that you find some best-practices guides to tune your network, servers, and storage devices for optimal performance. In many cases tuning is as simple as enabling jumbo frames or using link aggregation protocols to increase the bandwidth available to the storage device.
8. Choose the First Movers
Once you’ve built up your brand-spanking-new virtualization solution and tested it with a few new virtual servers, it’s time to start putting a production load on it. Start slow here, and plan an orderly transition from physical to virtual.
Pick a few smaller-scale physical servers, such as a lightly used application server, or even an Active Directory domain controller (assuming that you have multiple physical domain controllers) and either build them fresh on the virtual infrastructure or use P2V (physical-to-virtual) tools to move the server instance in its entirety. In the case of domain controllers, it’s always best to build them fresh; but you can easily transition application servers and other types to a virtual server with P2V tools, saving time and aggravation. However, you may encounter instances where these tools cannot successfully move a server, in which case you will have to rebuild it.
By starting with smaller servers first, you can flush out any problems that the new virtualized infrastructure may have before you move highly visible services over. Once you’re satisfied with the stability of the new arrangement, you can begin moving the heavier-duty servers over.
9. Watch Carefully
Once you’ve started the transition process, keep a close eye on the performance, on a virtual-server, physical-host, and storage level. If your setup has automated load leveling, make sure that it’s enabled and functional, and confirm that your original resource-utilization forecasts aren’t being eclipsed. It’s best if you can see possible resource problems on the horizon before you get there.
10. Enjoy All the New Capabilities
Now you can take advantage of all the goodies that virtualization has to offer. Use snapshots to preserve system states prior to updating sensitive code. Use cloning to quickly and easily spin up new server instances when you need them. Use live migrations to transition virtual servers from one host to another without downtime should you need to take down a physical server for maintenance. All that and more is now available, and if you've done everything right, it will save you time and money.