Recently I, along with thousands of other system administrators, have been swearing more than usual. If you're one of these people, you know why - the winsxs folder starts to use huge amounts of space on your hard disk. If you've gone by Microsoft recommended practice and created a 50GB C drive, then you also know how quickly this screws you.
Is there a way to reduce this folder? If you apply a Service Pack and go through the mechanism to apply it without chance of uninstalling it then you'll grab a little space back, but as you apply more updates, patches and new drivers the winsxs (or Windows side by side folder) will continue to grow. Theoretically it allows you to roll back if something goes wrong with some component of the operating system. In real life though, this isn't really done - we can just reinstall the busted component or whatever.
The system that controls the winsxs folder is tied to Windows Updates - and as we all know in Windows Vista, 7, 8, Server 2008, 2008R2 and 2012 Windows Updates can be hit and miss. Updates failing to apply, updates taking forever to apply or the ever annoying "Shutdown and install updates" that drags on forever. Vastly different to Windows XP of course.
Most often the fix is to replace the disk, or expand your hard disk size but this is frustrating and annoying. It's also expensive for our clients. Unfortunately it seems to be the best way to solve this issue - there is no short term fix or even any hint from Microsoft this will be solved.
I recommend that for new servers, a 100GB C drive is configured to give you breathing time until Microsoft finally manage to solve this issue. If you know better - hit the comments.