Back in the late 1990s and early 2000s, most of us in the SBC space dreamed of a Terminal Server feature called "live session migration." We wanted to be able to take a fully running user session from one server and instantly and transparently move it to another server. Unfortunately this feature never existed, and now that most of our RDSH and XenApp servers are virtual (with live migration capabilities), most of us forgot about our single session migration dreams.
A few weeks ago I had some beers with a couple of guys who talked about how live session migration for XenApp/TS/RDSH would actually be possible to do. They asked me if I thought they should build it into a product or if it was too late. I figured this would be a good idea for an article and an interesting conversation, so let's look at this today.
Why would you want live session migration?
The ability to move a live user session from one Terminal Server to another was huge in the days of physical servers. We liked this concept for several reasons, including:
- Towards the end of the day when you only have a few users left on each server, you could consolidate your users to a single server and power down the rest.
- You could move a "problem" user from one server to another. (For example if one user is taking up too much CPU, move him to a server that has more available.)
- Move users off of servers that need to be patched in order to provide 24x7 computing with no downtime.
Do we still need this today?
If this Terminal Server live session migration capability was suddenly available today, would we care? It could be interesting:
- Live migration allows us to move entire VMs from host-to-host today. With RDSH / TS / XenApp servers, sure we can consolidate users onto fewer physical hosts, though it's still not as efficient since there's a lot of extra overhead for each VM. Or do Moore's Law and the efficiencies of today's hypervisors make this point moot?
- Moving a problem user to a different server is still nice today, right? Or again, do Moore's Law and the protections built into current versions of Windows Server mean this isn't as important anymore?
And of course there's the whole trend I wrote about last week of single user desktop VMs potentially replacing RDSH / TS / XenApp sessions. If that happens then we essentially get "single user live migration" for free.
So what do you think? Would you like to see single user live session migration for RDSH / TS / XenApp? Or is it too late?