Index: sbin/hastd/parse.y
===================================================================
--- sbin/hastd/parse.y	(revision 223532)
+++ sbin/hastd/parse.y	(working copy)
@@ -293,11 +293,9 @@ yy_config_parse(const char *config, bool exitonerr
 			 */
 			curres->hr_replication = depth0_replication;
 		}
-		if (curres->hr_replication == HAST_REPLICATION_MEMSYNC ||
-		    curres->hr_replication == HAST_REPLICATION_ASYNC) {
-			pjdlog_warning("Replication mode \"%s\" is not implemented, falling back to \"%s\".",
-			    curres->hr_replication == HAST_REPLICATION_MEMSYNC ?
-			    "memsync" : "async", "fullsync");
+		if (curres->hr_replication == HAST_REPLICATION_MEMSYNC) {
+			pjdlog_warning("Replication mode \"memsync\" is not implemented, falling back to \"%s\".",
+			    "fullsync");
 			curres->hr_replication = HAST_REPLICATION_FULLSYNC;
 		}
 		if (curres->hr_checksum == -1) {
Index: sbin/hastd/activemap.c
===================================================================
--- sbin/hastd/activemap.c	(revision 223532)
+++ sbin/hastd/activemap.c	(working copy)
@@ -671,7 +671,30 @@ activemap_need_sync(struct activemap *amp, off_t o
 	return (modified);
 }
 
+/*
+ * Mark dirty extents for synchronization.
+ */
 void
+activemap_mark_sync(struct activemap *amp)
+{
+	int ext;
+
+	assert(amp->am_magic == ACTIVEMAP_MAGIC);
+
+	bit_ffs(amp->am_memmap, amp->am_nextents, &ext);
+	if (ext == -1) {
+		/* There are no dirty extents, so we can leave now. */
+		return;
+	}
+	for (; ext < amp->am_nextents; ext++) {
+		if (bit_test(amp->am_memmap, ext)) {
+			bit_set(amp->am_syncmap, ext);
+			amp->am_memtab[ext] = ext2reqs(amp, ext);
+		}
+	}
+}
+
+void
 activemap_dump(const struct activemap *amp)
 {
 	int bit;
Index: sbin/hastd/activemap.h
===================================================================
--- sbin/hastd/activemap.h	(revision 223532)
+++ sbin/hastd/activemap.h	(working copy)
@@ -63,6 +63,7 @@ void activemap_sync_rewind(struct activemap *amp);
 off_t activemap_sync_offset(struct activemap *amp, off_t *lengthp,
     int *syncextp);
 bool activemap_need_sync(struct activemap *amp, off_t offset, off_t length);
+void activemap_mark_sync(struct activemap *amp);
 
 void activemap_dump(const struct activemap *amp);
 
Index: sbin/hastd/primary.c
===================================================================
--- sbin/hastd/primary.c	(revision 223532)
+++ sbin/hastd/primary.c	(working copy)
@@ -1202,12 +1202,22 @@ ggate_recv_thread(void *arg)
 				res->hr_stat_flush++;
 				break;
 			}
-			pjdlog_debug(2,
-			    "ggate_recv: (%p) Moving request to the send queues.",
-			    hio);
-			refcount_init(&hio->hio_countdown, ncomps);
-			for (ii = 0; ii < ncomps; ii++)
-				QUEUE_INSERT1(hio, send, ii);
+			if (res->hr_replication != HAST_REPLICATION_ASYNC) {
+				pjdlog_debug(2,
+				    "ggate_recv: (%p) Moving request to the send queues.",
+				    hio);
+				refcount_init(&hio->hio_countdown, ncomps);
+				for (ii = 0; ii < ncomps; ii++)
+					QUEUE_INSERT1(hio, send, ii);
+			} else {
+				pjdlog_debug(2,
+				    "ggate_recv: (%p) Moving request to the local send queue.",
+				    hio);
+				refcount_init(&hio->hio_countdown, 1);
+				/* Local component is 0 for now. */
+				ncomp = 0;
+				QUEUE_INSERT1(hio, send, ncomp);
+			}
 			break;
 		}
 	}
@@ -1685,7 +1695,8 @@ ggate_send_thread(void *arg)
 			else
 				ggio->gctl_error = hio->hio_errors[0];
 		}
-		if (ggio->gctl_error == 0 && ggio->gctl_cmd == BIO_WRITE) {
+		if (res->hr_replication != HAST_REPLICATION_ASYNC &&
+		    ggio->gctl_error == 0 && ggio->gctl_cmd == BIO_WRITE) {
 			mtx_lock(&res->hr_amp_lock);
 			activemap_write_complete(res->hr_amp,
 			    ggio->gctl_offset, ggio->gctl_length);
@@ -2124,6 +2135,30 @@ guard_one(struct hast_resource *res, unsigned int
 		rw_unlock(&hio_remote_lock[ncomp]);
 		pjdlog_debug(2, "remote_guard: Connection to %s is ok.",
 		    res->hr_remoteaddr);
+		if (res->hr_syncsrc != HAST_SYNCSRC_SECONDARY  &&
+		    res->hr_replication == HAST_REPLICATION_ASYNC) {
+			/*
+			 * Bump local count and start synchronization.
+			 */
+			ncomp = 1;
+			mtx_lock(&metadata_lock);
+			if (activemap_ndirty(res->hr_amp) > 0) {
+				activemap_mark_sync(res->hr_amp);
+				if (res->hr_primary_localcnt ==
+				    res->hr_secondary_remotecnt) {
+					res->hr_primary_localcnt++;
+					pjdlog_debug(1,
+					    "Increasing localcnt to %ju.",
+					    (uintmax_t)res->hr_primary_localcnt);
+					(void)metadata_write(res);
+				}
+				mtx_unlock(&metadata_lock);
+				res->hr_syncsrc = HAST_SYNCSRC_PRIMARY;
+				sync_start();
+			} else {
+				mtx_unlock(&metadata_lock);
+			}
+		}
 		return;
 	}