diff --git a/lib/kadm5/iprop.8 b/lib/kadm5/iprop.8
index 832041011..a4b4e1e70 100644
--- a/lib/kadm5/iprop.8
+++ b/lib/kadm5/iprop.8
@@ -64,19 +64,14 @@
 .Op Fl Fl version
 .Op Fl Fl help
 .Nm ipropd-slave
-.Oo Fl c Ar string \*(Ba Xo
-.Fl Fl config-file= Ns Ar string
-.Xc
-.Oc
-.Oo Fl r Ar string \*(Ba Xo
-.Fl Fl realm= Ns Ar string
-.Xc
-.Oc
-.Oo Fl k Ar kspec \*(Ba Xo
-.Fl Fl keytab= Ns Ar kspec
-.Xc
-.Oc
+.Oo Fl c Ar string \*(Ba Xo Fl Fl config-file= Ns Ar string Xc Oc
+.Oo Fl r Ar string \*(Ba Xo Fl Fl realm= Ns Ar string Xc Oc
+.Oo Fl k Ar kspec \*(Ba Xo Fl Fl keytab= Ns Ar kspec Xc Oc
+.Op Fl Fl statusfile= Ns Ar file
+.Op Fl Fl hostname= Ns Ar hostname
+.Op Fl Fl port= Ns Ar port
 .Op Fl Fl time-lost= Ns Ar time
+.Op Fl Fl async-hdb
 .Op Fl Fl detach
 .Op Fl Fl version
 .Op Fl Fl help
@@ -151,17 +146,19 @@ Supported options for
 .It Fl c Ar string , Fl Fl config-file= Ns Ar string
 .It Fl r Ar string , Fl Fl realm= Ns Ar string
 .It Fl k Ar kspec , Fl Fl keytab= Ns Ar kspec
-keytab to get authentication from
+Keytab for authenticating
+.Nm ipropd-slave
+clients.
 .It Fl d Ar file , Fl Fl database= Ns Ar file
 Database (default per KDC)
 .It Fl Fl slave-stats-file= Ns Ar file
-file for slave status information
+File for slave status information.
 .It Fl Fl time-missing= Ns Ar time
-time before slave is polled for presence (default 2 min)
+Time before slave is polled for presence (default 2 min).
 .It Fl Fl time-gone= Ns Ar time
-time of inactivity after which a slave is considered gone (default 5 min)
+Time of inactivity after which a slave is considered gone (default 5 min).
 .It Fl Fl detach
-detach from console
+Detach from console.
 .It Fl Fl version
 .It Fl Fl help
 .El
@@ -172,11 +169,20 @@ Supported options for
 .It Fl c Ar string , Fl Fl config-file= Ns Ar string
 .It Fl r Ar string , Fl Fl realm= Ns Ar string
 .It Fl k Ar kspec , Fl Fl keytab= Ns Ar kspec
-keytab to get authentication from
+Keytab with client credentials for authenticating to
+.Nm ipropd-master .
+.It Fl Fl status-file= Ns Ar file
+.It Fl Fl hostname= Ns Ar hostname
+Hostname for client principal if different from actual hostname.
+.It Fl Fl port= Ns Ar port
 .It Fl Fl time-lost= Ns Ar time
 time before server is considered lost (default 5 min)
+.It Fl Fl async-hdb
+Use asynchronous writes.
+This is very useful for very busy sites or sites with very large
+HDBs.
 .It Fl Fl detach
-detach from console
+Detach from console.
 .It Fl Fl version
 .It Fl Fl help
 .El
diff --git a/lib/kadm5/ipropd_slave.c b/lib/kadm5/ipropd_slave.c
index 9a6387667..ec8b3f047 100644
--- a/lib/kadm5/ipropd_slave.c
+++ b/lib/kadm5/ipropd_slave.c
@@ -38,6 +38,7 @@ RCSID("$Id$");
 static const char *config_name = "ipropd-slave";
 
 static int verbose;
+static int async_hdb = 0;
 
 static krb5_log_facility *log_facility;
 static char five_min[] = "5 min";
@@ -431,18 +432,18 @@ receive(krb5_context context,
         kadm5_server_context *server_context)
 {
     krb5_error_code ret, ret2;
+    HDB *mydb = server_context->db;
 
-    ret = server_context->db->hdb_open(context,
-				       server_context->db,
-				       O_RDWR | O_CREAT, 0600);
+    ret = mydb->hdb_open(context, server_context->db, O_RDWR | O_CREAT, 0600);
     if (ret)
         krb5_err(context, IPROPD_RESTART_SLOW, ret, "db->open");
 
+    (void) mydb->hdb_set_sync(context, mydb, !async_hdb);
     ret2 = receive_loop(context, sp, server_context);
     if (ret2)
 	krb5_warn(context, ret2, "receive from ipropd-master had errors");
 
-    ret = server_context->db->hdb_close(context, server_context->db);
+    ret = mydb->hdb_close(context, server_context->db);
     if (ret)
         krb5_err(context, IPROPD_RESTART_SLOW, ret, "db->close");
 
@@ -598,7 +599,7 @@ receive_everything(krb5_context context, int fd,
 
     reinit_log(context, server_context, vno);
 
-    ret = mydb->hdb_set_sync(context, mydb, 1);
+    ret = mydb->hdb_set_sync(context, mydb, !async_hdb);
     if (ret)
         krb5_err(context, IPROPD_RESTART_SLOW, ret, "failed to sync the received HDB");
     ret = mydb->hdb_close(context, mydb);
@@ -701,6 +702,7 @@ static struct getargs args[] = {
       "private argument, do not use", NULL },
     { "pidfile-basename", 0, arg_string, &pidfile_basename,
       "basename of pidfile; private argument for testing", "NAME" },
+    { "async-hdb", 'a', arg_flag, &async_hdb, NULL, NULL },
     { "hostname", 0, arg_string, rk_UNCONST(&slave_str),
       "hostname of slave (if not same as hostname)", "hostname" },
     { "verbose", 0, arg_flag, &verbose, NULL, NULL },