HDX Plug-n-Play for USB storage is one of Citrix's HDX/High Definition eXperience features introduced in XenApp 5 Feature Pack 2. With this feature your users have the ability to plug-in their USB thumb drive/USB stick and use it with their XenApp delivered application. 

Can users now have a local-like experience when interacting with a USB stick or USB disk drive? Hurrah! Users will love it.

Until you show it to users...

And then, well.. there's often no pleasing users.

Citrix have stated that with HDX Plug-n-Play for USB a user's USB access can be at any time; before launching the application or while they are in the middle of working with the application.

Granted, prior to Feature Pack 2, USB drive access for XenApp and its forefathers was a pain. You know the scenario,  you're working with Microsoft Word delivered to you via XenApp, you want to load up some pictures, or save the data to a USB stick like you do on a PC. But , prior to FP2 this wasn't straightforward.

By default, you were only permitted to enumerate USB drives at logon. So, for a Citrix published app you'd potentially have to save the file, log off, put your USB stick in the device, log on to Citrix again, open the file, and then save to your USB drive.

Not pretty.

You could, if you had a win32 client, make use of the Dynamic USB utility. This was slightly better than the default: you had to have it preconfigured, and it did have some pre-reqs. You installed the component on the end device, which had to have NTFS. The utility created a linked directory onto your device - which you could then map dynamically while in a session. Again - not entirely beautiful. It required a bit of effort to set up, it required a bit of understanding from the user - but it did work.

With FP2, HDX Plug-n-Play for USB storage devices is enabled by default. As long as you've a v11 win32 or Linux client you're good to go. Bear in mind you've also the thin clients that support HDX   

So everything is dandy - USB storage devices are enabled by default, you've an HDX ready device - you launch your Word application, plug in your USB stick, select 'file save as' and there it is "D$ on Drive V:" or whatever drive mapping you've been assigned.Pretty good: more dynamic - would have been more friendly to have the USB drive name but you roll with the punches. Far less effort than logging off and logging on, much less faff than preconfiguring the Dynamic USB utility. 

However, bear in mind the words of the documentation

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• U3 smart drives and devices with similar autorun behavior
• Explorer.exe published as a seamless application

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The last part is an important Fact - "Explorer as a published seamless application". Note what we tested - we opened Word, we added our USB stick, we looked at the file dialgoue box and saw our drive.This would have worked for a variety of apps - IE and 'save as', notepad, Excel, Powerpoint, etc. etc.

But, say the user had launched 'Explorer' which we'd created as a published application, or 'My Documents' (which is essentially Explorer in a specific location), as a published application. They had done this because they're expecting to transfer their photos that they've taken on a site visit to a document store, or they want to copy some files en masse - not an unusal request -  HDX plug and play will not work. 

No matter how many times they press 'refresh' and pop the USB stick in and out, the USB drive won't appear.

It is not "broken". That's as is. In this situation, you'd have to plug in the USB drive then launch Explorer. There's a slight saving grace in the log-on time, for the latest v11.2 online client (PNAgent), is very quick.

So -  HDX Plug-n-Play for USB is a good feature. Supporting users who need to use USB sticks is far less cumbersome now than it has ever been; it allows users of thin clients (that are HDX ready) to have a more PC like experience; and, it is available for more clients than just win32. But, it is not always "local-like experience when interacting with a USB stick or USB disk drive", it is not "anytime".

Bear that in mind, and set your user's expectations accordingly.