If you need to mass start your virtual servers, run the following code in SSH on the host:
Xen PV/HVM
START CFGS=/home/xen/vm*/;for cfg in $CFGS;do xm create $cfg*.cfg;done STOP xm shutdown -aw
OpenVZ
START CFGS=`vzlist -S -Ho ctid`;for cfg in $CFGS;do vzctl start $cfg;done STOP CFGS=`vzlist -S -Ho ctid`;for cfg in $CFGS;do vzctl stop $cfg;done
KVM
CFGS=/home/kvm/kvm*/;for cfg in $CFGS;do virsh create $cfg*.xml;done