@dcskinner @olivierlambert
You can read key/values from the xenstore, and write some (from VM to outside), but you cannot write values "in live" from outside the VM to the inside.
It is, but XAPI doesn't provide a interface for it.
do the guest tools quiesce the filesystems before snapshotting?
Tools are aware of a snapshot so you don't have blocks in flight.
do the guest tools quiesce the filesystems before snapshotting?
Guests kernel are aware, as it is them that are performing a "suspend" on toolstack request (thus quiece filesystems); although "tools" can only observe that the system has been suspended after the fact by measuring side effects, and not orchestrate it.
It's because suspend/resume operation doesn't come from "guest tools" actually, but instead from the kernel drivers. So userland tools has no say on it.