It would be nice, if XenServer would offer some easy-to-use option, to enlarge SRs, after new space has been added to storage (ideally added to XenCenter via XAPI - so also easy to adapt for other projects/managements).
All scale up storage-systems will come to a point, where someone just adds storage space and that ends up with manually 'fixing' the SR-size.
Last time I needed to delete the partition and recreate a bigger one (where the data inside survived). It worked, but it didn't feel quite good to do that (by hand).
I currently can't say how VMware solves it, Windows just has a GUI to extend, which is quickly done and idiot-safe.