@User-cxs Hey 
That's a bit hard to tell just from that what's happening 
You might get some clues from your logs on /var/log/SMlog. If you get something bad from here, it means there is an issue with the storage stack.
If you get nothing, maybe it's an issue at the xapi command itself, you might want to look at /var/log/xensource.log.
Hope that can help you 