[libvirt-users] live migration

Hello, everybody.     I use NFS to do live migration。After input  virsh --connect=qemu:///system --quiet migrate --live vm12 qemu+tcp://pcmk-1/system  (vm12  is vm name,/pcmk-1 is host name)it use almost 10s for preparation. During the 10s,the vm is still runing and can ping other vm. But if i input mkdir pcmk-6 in vm during the 10s,it say :mkdir: cannot create directory `pcmk-6': Read-only file system.     Anybody can tell me this situation is due to my wrong configure or libvirt cannot mkdir during migration？thanks!