Before setting up a new Windows 2003 server, I had to do something I hadn't done in quite a while: I actually had to hunt for an installation CD. I've gotten so used to setting up virtual machines (VMs) and using ISO files that when it came time for building a non-virtual, physical server, the whole process seemed archaic. It occured to me how easy virtualization has made my job.
Administration habits for virtual servers can be dramatically different from those of physical servers. For example, I'm sure all of us at some point have tried doing CTRL-ALT-INS on our physical systems instead of CTR-ALT-DEL and wondered why the login window didn't appear. Similarly, have you ever tried to take a snapshot of a server only to realize it was physical and you could not? Virtual servers offer so much more flexibility over physical ones that administration becomes much simpler and far less time consuming. In this tip, I will highlight some of the ways that virtualization makes administration simpler.
Snapshots create point-in-time images of servers. This valuable tool is a lifesaver when an application upgrade or operating system patch causes a server or application crash. You can restore from a previous state in minutes compared to a complicated physical server tape backup, which can take hours. The Snapshot Manager included with VMware ESX and Workstation creates multiple snapshots to preserve a server at various points in time (Server only creates a single snapshot at a time). If you need to revert a virtual machine back to a specific snapshot but not all the way back to the beginning state, this function can be very beneficial.
Managing server hardware is an area where virtual servers have much greater flexibility over physical servers. Because VM hardware is virtual, one can easily add and remove memory, network cards, CPUs and disks at any time. This type of flexibility saves money compared with physical server purchases, which often include more memory and disk space than is actually needed. After you install applications and start using a physical server, you may find that the server with 4 GB of memory and 300 GB of disk space is using less then 2 GB of RAM and 30 GB of disk space. That's a lot of wasted resources that could have been used for something else. It's a best practice to give your VMs only the resources they need. The flexibility of VMware allows for this, since you can easily up the resources later, as needed.
When our CIO approved the funds for the new hardware and VMware software needed for our server virtualization project, he jokingly stated that we couldn't buy any new hardware for five years. Virtualization offers the flexibility to easily provision new servers as needed without buying new hardware (provided virtual servers are sized for growth). No longer do you need to buy more physical hardware every time a new server is required. A new virtual server can be built in less then an hour, compared with the several days necessary to order, receive and configure new hardware.
Server disk management is much easier and more flexible compared to physical systems. You can easily expand an existing disk or add additional disks as needed. Also, if you have an issue with a virtual disk on one server, you can easily attach the virtual disk to another VM as an additional drive to resolve the problem. You can also copy whole virtual disk (VMDK) files to another storage system to have a whole system backup of your server. This is commonly done with scripts by creating a snapshot of the server to suspend writes to the original disk file and then copying the disk file and deleting the snapshot when the copy completes. ESX 3.5 introduced the new Storage vMotion feature, which allows virtual disk files to be moved to other datastores while the VM is powered on (in previous versions, the VM had to be powered off.)
Installing operating systems and applications on your virtual servers is much simpler and faster then physical servers, thanks to ISO files, a method of mounting virtual CD-ROMs on virtual machines. Maintaining a library of physical discs for all your server operating systems and applications is a thing of the past. It is much easier to mount an ISO file than it is to find the physical CD-ROM you need and put it in the server. I create a central repository of ISO files for all my various operating systems and applications that my VMs can easily access whenever they need to.
Increased server availability and uptime is an added benefit to virtualizing servers when utilizing a feature such as VMware HA. HA, or high availability, offers a reasonably inexpensive and simple method for protecting virtual machines from hardware failure. If a major component fails in a physical server, the system is down until the component is replaced. This can take hours or days. With HA, if you have a failure with the physical host, virtual machines simply restart on another physical ESX host within minutes of the failure. ESX 3.5 detects operating system failures such as blue screens to automatically restart your VM.
To create duplicate copies of servers, virtualization provides the convenience of cloning. A server clone is useful for troubleshooting or testing upgrades without affecting the original server. Also, cloning lets you easily create new VMs without having to re-install the operating system and applications. This is particularly useful for creating development, testing and production environments, since they are usually identical to each other. For those using VMware, the cloning feature is built into VirtualCenter. To clone a virtual machine, power off the VM and select the clone menu option. If you do not have VirtualCenter, you can manually clone a server by using the Vmkfstools command line utility that comes with ESX.
These are just some of the features that make living in a virtual world a lot better than a physical one. When it comes to administration and procedures, virtualization requires a change, but it is definitely a change for the better.
About the author: Eric Siebert is a 25-year IT veteran with experience in programming, networking, telecom and systems administration. He is a guru-status moderator on the VMware community VMTN forum and maintains VMware-land.com, a VI3 information site.