1. Health Monitoring and Recovery

HMR performs two functions:
a. It conducts tests against the servers in your farms.
b. If a particular test fails, it performs some action.
PS 4.5 has some preconfigured tests. You can use the SDK to write our own tests. It can perform tests such as performing a sample logon, making a request to the IMA service, requesting a Citrix XML ticket, or enumerating a list of terminal services sessions. You can configure these tests to run as often as you want. If any test fails, the system can perform a certain action. This action might be as simple as writing an item to the event
log. You can also configure actions that restart the Citrix IMA service, remove the server from load-balancing, or even reboot a server.

One of the cool things is that while you configure multiple tests on individual or groups of servers in your farm, you can also set a farm-wide “safety net” that specifies a certain maximum percentage of servers that can be automatically taken offline by HMR. (By
default this is 10 %.) This prevents one poorly-written test from accidentally
taken your entire farm offline.

2. Administrator Configuring Logging

You can configure a separate, stand-alone database that logs every single change that’s made to the data store by an administrator. This database hooks in at the IMA service level, so it picks up all changes—regardless of whether they were invoked via the Java console, the MMC, a CPSCOM (previously MFCOM) script, or a command-line tool. The reports will be in basic HTML form accessible via the MMC reports centre.

3. Application Isolation Environment engine

Citrix first introduced Application Isolation Environments (AIEs) in PS 4. This technology lets us to install multiple applications on a single server that ordinarily conflict with each other. In PS4, the overhead of using AIE was huge, and it really slowed things down when it was in use. AIE technology in PS 4.5 has been majorly overhauled

4. Application Streaming

A PS 4.5 server can also be a Citrix Streaming Server, meaning it can stream applications down to non-Presentation Server Windows workstations. A PS 4.5 server can be a Citrix Streaming Server client, meaning you can use another Citrix Streaming Server to stream applications to the Presentation Server instead of manually installing the applications or
using IM.

5. ICA Display Enhancements

PS4.5 has a couple of features that should make ICA perform a bit better in certain situations.

SpeedScreen Progressive Display: A sixth technology was added to the Speed Screen line-up for PS 4.5 called Progressive Display. When enabled, highly-complex graphical
items in motion can temporarily be sent to the client at a lower resolution so that they can be displayed in real time. Once the motion stops, the image will “snap” back up to the full resolution. This means that the user can get a good interactive experience while scrolling or moving an on-screen object.

Improved Tossing and Queuing Algorithm: In some situations, there would be more screen updates going from a Presentation Server to a client than the network could handle. In this case, the ICA protocol driver on the server would send as many packets as it could to the client, but when it got behind, it would randomly drop bits of the screen as it tried to keep up. The result was that screen motions looked choppy and weird. In PS 4.5, the ICA protocol driver on the server has an improved technique for deciding which graphical elements can be discarded (tossed) and which should be held and sent together to the client (queuing).

6. Logon Throttling

The logon process has always been very resource intensive for a Citrix Presentation Server. The server can hang just by more than a few users logging in at the exact same time. The new load evaluator rule in PS 4.5 lets us to specify the “resource cost” of a user logon. You can use this rule to temporarily show a server as “full” whenever the
logon rate exceeds a set level.

7. Component Updates

Along with PS4.5, Citrix is updating Web Interface to 4.5 and ICA clients to Version 10.

What didn’t change?

Printing (Same engine as PS 4, but of course with all the hotfixes “built in.)
Licensing
Policies (Several new policy items, but everything else is the same)
Resource Manager (You can apply templates to servers to make them easier to configure)
Installation Manager (You can install applications into Isolation Environments with IM)