I   make a new volume with follow:
vxassist -g oradata -U fsgen make voldata 100000m layout=nolog oradata01
vxassist -g oradata mirror voldata layout=nolog oradata02
and add DCO20 with follow:
but when system crash cannot fastresync, must all disk resync.when resync complete I delete and add DCO20 again with follow :
#vxvol -g oradata set fastresync=off voldata
# vxvol -g oradata set drl=off voldata
# vxsnap -g oradata unprepare voldata
# vxsnap -g oradata prepare voldata drl=on

then when system crash it can fastresync.why ?help me please ! thanks!

My system is HPUX11.23 and My VXVM is 5.0MP1