compaction changed to .idx based deletion

weed/command/backup.go

@@ -121,7 +121,7 @@ func runBackup(cmd *Command, args []string) bool {
 	}
 
 	if v.SuperBlock.CompactionRevision < uint16(stats.CompactRevision) {
-		if err = v.Compact(0, 0); err != nil {
+		if err = v.Compact2(30 * 1024 * 1024 * 1024); err != nil {
 			fmt.Printf("Compact Volume before synchronizing %v\n", err)
 			return true
 		}