Wednesday, August 10, 2005

ZEN and the art of Terminal Server Farm architecture

We're doing some pretty damned cool stuff with Win2K Terminal Services lately. When it's all said and done, we'll have basically Citrix-equivalent load balancing and application "publishing" capabilities, at a fraction of the cost. ZENworks really does make this powerfully simple - if you know what you're doing.

Imagine logging into an RDP session, and seeing only a Novell Application Launcher window with all of your apps. Internet explorer is there, but you can't browse to or run anything but a legitimate internet URL. Same with Windows explorer. You can add your own network printers to your session, but the printers at your location automatically appear each time you log in. If you need to use an application that hasn't been installed, it automatically installs and configures itself for you.

Behind the scenes, there are no roaming profiles. No group policies governing behavior or lock-down. No published applications. No Novell Client. There's not even eDirectory - that's been installed into a separate tree, being accessed by the ZDM middle-tier service. No local administrator requirement for application installs. One password to remember, thanks to DirXML. No Citrix. No hardware load balancers. Just one system acting as a load balancer/proxy for RDP, and five AD member-servers running Terminal Services. In fact, I can scale this architecture as fast as I can image new IBM BladeCenter HS20 systems, until the proxy system breaks. I put that point at over 1,000 users, which we won't get near for quite some time. At our expected load of 400 - 500, we should be flush.

For us, it will save $100k the first year, and $25k each following year for Citrix licensing. This doesn't include sunk costs in existing Citrix licenses, which we don't have enough of to facilitate short-term growth. We replace those costs with about $40k of new ZDM licensing, and roughly $8k / year in maintenance. Anymore, Citrix's only true value-add is robust load balancing in large farms, and seamless application windows. Certainly not enough to justify their exorbitant licensing costs. I know they cram a lot of products into the bundle, but I bet if they sold those features a la carte, many of their more experienced customers would reconsider what they've been buying.

Sadly, Novell Support told us that basically it couldn't be done. Shows what we know.


Jeremy said...

This sounds great. What part did Novell say couldn't be done?

We have Citrix and Zen 4 and I'm forever asking our MS team why we don't use Zen on our Citrix Servers.

ZEN Master said...

We were originally told that you couldn't push apps to a Terminal Server using NAL. Eventually they realized you could in fact do that.

The issue we're working on with Novell now involves distributing applications when the source files exist on a network share. Without the Novell client, this fails. They've provided us a DLL that fixes the issue - look for it in a ZEN 6.5 support pack.

I'd really recommend use of ZDM 6.5, but you can get ZEN 4 to work. Again, depending on your needs, you may be able to eliminate your Citrix licenses.

We're currently in production with this system (mid-deployment). Over 200 users on-line, with more coming in every day as we roll out. A few minor kinks, but nothing we haven't been able to address.