Detail steps as  follow:

1. create a cache object

# vxasssist –g dgname make volcache1 1500g
# vxmake -g dgname cache cobj cachevolname=volcache1

# vxcache -g dgname start cobj
 

2.prepare snapshot for original data volume

#vxsnap -g dgname prepare vol

3.create snapshot

# vxsnap -g dgname make source=vol/newvol=sosvol/cache=cobj

After finish fullfsck, if you like to restore  original state, you can use snapshot restore :
4.when need restore:
#vxsnap -g dgname restore vol source=sosvol