This patch from Sami Farin lets you specify --fsync if you want fsync()
to be called on every file we write.

--- orig/options.c	2004-08-11 23:42:23
+++ options.c	2004-07-03 20:18:13
@@ -38,6 +38,7 @@ int make_backups = 0;
  **/
 int whole_file = -1;
 
+int do_fsync = 0;
 int archive_mode = 0;
 int keep_dirlinks = 0;
 int copy_links = 0;
@@ -240,6 +241,7 @@ void usage(enum logcode F)
   rprintf(F," -b, --backup                make backups (see --suffix & --backup-dir)\n");
   rprintf(F,"     --backup-dir            make backups into this directory\n");
   rprintf(F,"     --suffix=SUFFIX         backup suffix (default %s w/o --backup-dir)\n",BACKUP_SUFFIX);
+  rprintf(F,"     --fsync                 fsync every written file\n");
   rprintf(F," -u, --update                update only (don't overwrite newer files)\n");
   rprintf(F,"     --inplace               update destination files inplace (SEE MAN PAGE)\n");
   rprintf(F," -K, --keep-dirlinks         treat symlinked dir on receiver as dir\n");
@@ -346,6 +348,7 @@ static struct poptOption long_options[] 
   {"safe-links",       0,  POPT_ARG_NONE,   &safe_symlinks, 0, 0, 0 },
   {"help",            'h', POPT_ARG_NONE,   0,              'h', 0, 0 },
   {"backup",          'b', POPT_ARG_NONE,   &make_backups, 0, 0, 0 },
+  {"fsync",            0,  POPT_ARG_NONE,   &do_fsync, 0, 0, 0 },
   {"dry-run",         'n', POPT_ARG_NONE,   &dry_run, 0, 0, 0 },
   {"sparse",          'S', POPT_ARG_NONE,   &sparse_files, 0, 0, 0 },
   {"cvs-exclude",     'C', POPT_ARG_NONE,   &cvs_exclude, 0, 0, 0 },
@@ -1069,6 +1072,9 @@ void server_options(char **args,int *arg
 		args[ac++] = tmpdir;
 	}
 
+	if (do_fsync && am_sender)
+		args[ac++] = "--fsync";
+
 	if (compare_dest && am_sender) {
 		/* the server only needs this option if it is not the sender,
 		 *   and it may be an older version that doesn't know this
--- orig/receiver.c	2004-08-03 15:34:32
+++ receiver.c	2004-07-16 20:13:31
@@ -36,6 +36,7 @@ extern int preserve_hard_links;
 extern int preserve_perms;
 extern int cvs_exclude;
 extern int io_error;
+extern int do_fsync;
 extern char *tmpdir;
 extern char *partial_dir;
 extern char *compare_dest;
@@ -309,6 +310,12 @@ static int receive_data(int f_in, char *
 		exit_cleanup(RERR_FILEIO);
 	}
 
+	if (do_fsync && (fd != -1) && (fsync(fd) != 0)) {
+		rsyserr(FERROR, errno, "fsync failed on %s",
+			full_fname(fname));
+		exit_cleanup(RERR_FILEIO);
+	}
+
 	sum_end(file_sum1);
 
 	if (mapbuf)
--- orig/util.c	2004-08-11 23:42:23
+++ util.c	2004-07-03 20:18:13
@@ -33,6 +33,7 @@ extern int module_id;
 extern int modify_window;
 extern char *partial_dir;
 extern struct exclude_list_struct server_exclude_list;
+extern int do_fsync;
 
 int sanitize_paths = 0;
 
@@ -298,6 +299,12 @@ int copy_file(char *source, char *dest, 
 		return -1;
 	}
 
+	if (do_fsync && fsync(ofd) < 0) {
+		rsyserr(FERROR, errno, "fsync failed on %s",
+			full_fname(dest));
+		return -1;
+	}
+
 	return 0;
 }