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The Beauties and Pitfalls of Virtual Machines

Thursday, September 16, 2010 in Technical Articles (Views: 3448)
A lot of things have changed in technology over the years, but despite incremental software upgrades, or just faster computers that software writes bigger "bloatware" for, there are some things that stand out as great advancements.

It's hard not to love virtual computing, and one of the great advancements in technology has been the use of Virtual Machines. Despite your platform of choice, it's easy - backups are a single file for a hard drive, and can be easily restored with a copy. If the host machine blows up, just recreate the virtual environment with the virtual disks.

Of course, you never get something for nothing, and virtual computing will cause major performance problems if it is not taken care of correctly. A couple of quick tips I've learned to enhance performance (not exactly sure any of these are on the "best practice" list, just what I've noticed).

My platform of choice is Hyper-V running on (at the time of writing) Windows 2008 R2.

Here are some tricks:

• Starting wth Windows 2008 R2, compressed VHD files are no longer allowed. To this, I say "bummer". Most of my disks compressed well, and the machines actually seemed to run better when the files were compressed. You can, however, backup your VHD files to compressed folders. For those of you who have unimportant test machines and wanted to save space, this can be a blow.
• Use physical disks when possible, especially for heavier processing. One such example, is my SQL server. It has its own hard drive for data files and backups, which also keeps the VHD sizes from growing to insane proportions, when a lot of it is just slack space. You'll see some results almost immediately, one example for me was moving the Sharepoint content and my SMS database to a physical disk, it made a world of difference.
• Use a seperate NIC for VM processing whenever possible. One example here is I have a dedicated NIC for the host OS, one for the backup server, and another for the other VMs. You'll find this will help your case. Just make sure that the virtual NICs do not share with the host OS and that you do not have DNS configured for it.
• Snapshots take up a lot of resources, and are not intended to be backups. Once you use them, delete them and merge your disks. This is one for those who created a snapshot 6 months ago and have a 100GB commit file that needs to be merged.

Anyway, I hope you find these tips useful - and happy virtual computing...


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