Fix of bug #417751 by Yasufumi Kinoshita.

storage/xtradb/srv/srv0start.c

@@ -1119,8 +1119,14 @@ innobase_start_or_create_for_mysql(void)
 
 		os_aio_use_native_aio = FALSE;
 	} else {
-		/* On Win 2000 and XP use async i/o */
-		os_aio_use_native_aio = TRUE;
+		/* On Win 2000 and XP currently native async i/o
+                   is not used for xtradb by default */
+		//os_aio_use_native_aio = TRUE;
+		os_aio_use_native_aio = FALSE;
+		fprintf(stderr,
+			"InnoDB: Windows native async i/o is disabled as default.\n"
+			"InnoDB:   It is not applicable for the current"
+			" multi io threads implementation.\n");
 	}
 #endif
 	if (srv_file_flush_method_str == NULL) {
@@ -1156,6 +1162,12 @@ innobase_start_or_create_for_mysql(void)
 	} else if (0 == ut_strcmp(srv_file_flush_method_str,
 				  "async_unbuffered")) {
 		srv_win_file_flush_method = SRV_WIN_IO_UNBUFFERED;
+		os_aio_use_native_aio = TRUE;
+		srv_n_read_io_threads = srv_n_write_io_threads = 1;
+		fprintf(stderr,
+			"InnoDB: 'async_unbuffered' was detected as innodb_flush_method.\n"
+			"InnoDB:   Windows native async i/o is enabled.\n"
+			"InnoDB:   And io threads are restricted.\n");
 #endif
 	} else {
 		fprintf(stderr,