With Virtual Desktop Infrastructure (VDI), IT administrators have some choices in terms of setup which can affect not only usability, but also security. Specifically, there is a choice between persistent VDI and non-persistent VDI as well as the hybrid persistent/non-persistent model.

As a recent article at BrianMadden.com about VDI and terminal servers (TS) points out, the concepts behind persistent and non-persistent operating systems apply not only to VDI, but also to TS and even physical desktops. But what are the differences between persistent, non-persistent and hybrid VDIs?

First of all, persistent desktops are desktop operating systems in which the file system is configured to be fully read/write-able. As such, the contents of the file system and the registry are persistent between OS reboots. One benefit of this is easier installation of hotfixes — by way of tools such as SCCM, or LanDesk — because when the OS is rebooted, those hotfixes are still in place.

However, one major drawback is that each system has its own persistent copy of its OS contents. Therefore, if each VDI desktop is a 50GB disk image, for example, storage requirements can quickly get out of hand.

Dell's Unidesk VDI solution is an example of a persistent VDI.

Non-persistent desktops, on the other hand, are desktop operating systems which are configured so that writes to the file system are not preserved. Some may be familiar with the term 'common image,' which refers to multiple desktops sharing the exact same image file and that term applies here. One major benefit of a non-persistent model is that, since the system reverts to its original state each boot, it's not a big deal if an end user deletes important files. One major downside of the non-persistent model is that every system will contain the exact same set of applications, while user-based preferences will be wiped out every reboot.

Atlantis' ILIO Diskless VDI solution is an example of a non-persistent VDI.

Lastly, hybrid VDI eliminates some of the weaknesses of non-persistent desktops by adding some persistence to the non-persistent model. A profile management solution, for example, can backup and restore user settings for Microsoft (News - Alert) Office and other key application. This allows the clean state of the desktop to be retained while allowing users some form of customization.

Obviously, there is no absolute solution, but one of these three models is likely to be the best fit depending on the situation.

To find out more about Jeff Kaplan and Breakthrough Technology Group , visit the company at ITEXPO. To be held Oct. 2-5 at the Austin Convention Center in Austin, TX, ITEXPO (News - Alert) offers an educational program to help corporate decision makers select the right IP-based voice, video, fax and unified communications solutions to improve their operations. Kaplan is speaking during “Cloud Desktops: Leveraging the Full Potential of the Cloud.” For more information on ITEXPO, click here.