diff --git a/sbin/dump/dump.8 b/sbin/dump/dump.8
index 13a69e42f677..40b257ab03a0 100644
--- a/sbin/dump/dump.8
+++ b/sbin/dump/dump.8
@@ -41,7 +41,7 @@
 .Nd filesystem backup
 .Sh SYNOPSIS
 .Nm dump
-.Op Cm 0123456789BbhfusTdWn Op Ar argument ...
+.Op Cm 0123456789BTWabcdfhnsu Op Ar argument ...
 .Op Ar filesystem
 .Sh DESCRIPTION
 .Nm Dump
@@ -56,7 +56,11 @@ option below for doing remote backups).
 A dump that is larger than the output medium is broken into
 multiple volumes.
 On most media the size is determined by writing until an
-end-of-media indication is returned.
+end-of-media indication is returned.  This can be enforced
+by using the
+.Cm a
+option.
+.Pp
 On media that cannot reliably return an end-of-media indication
 (such as some cartridge tape drives)
 each volume is of a fixed size;
@@ -85,8 +89,19 @@ level is 9.
 The number of dump records per volume.
 This option overrides the calculation of tape size
 based on length and density.
+.It Cm a
+.Dq auto-size .
+Bypass all tape length considerations, and enforce writing
+until an end-of-media indication is returned.  This fits best
+for most modern tape drives.  Use of this option is particularly
+recommended when appending to an existing tape, or using a tape
+drive with hardware compression (where you can never be sure about
+the compression ratio).
 .It Cm b Ar blocksize
 The number of kilobytes per dump record.
+.It Cm c
+Change the defaults for use with a cartridge tape drive, with a density
+of 8000 bpi, and a length of 1700 feet.
 .It Cm h Ar level
 Honor the user
 .Dq nodump
@@ -325,10 +340,12 @@ Each reel requires a new process, so parent processes for
 reels already written just hang around until the entire tape
 is written.
 .Pp
-restore(8) is currently unable to restore dumps that were created
-with a blocksize larger than 32 on some tape drives.  This is likely
-a bug in the tape driver.  Workaround for safety reasons: 
-dump aborts with an error message when choosing a blocksize > 32.
+Currently,
+.Xr physio 9
+slices all requests into chunks of 64 KB.  Therefore, it is
+impossible to use a larger tape blocksize, so
+.Nm dump
+will prevent this from happening.
 .Pp
 .Nm Dump
 with the
diff --git a/sbin/dump/dump.h b/sbin/dump/dump.h
index 4b2330e93a3b..0da4c28ec482 100644
--- a/sbin/dump/dump.h
+++ b/sbin/dump/dump.h
@@ -74,6 +74,7 @@ long	tsize;		/* tape size in 0.1" units */
 long	asize;		/* number of 0.1" units written on current tape */
 int	etapes;		/* estimated number of tapes */
 int	nonodump;	/* if set, do not honor UF_NODUMP user flags */
+int	unlimited;	/* if set, write to end of medium */
 
 int	notify;		/* notify operator flag */
 int	blockswritten;	/* number of blocks written on current tape */
diff --git a/sbin/dump/main.c b/sbin/dump/main.c
index 62d1caf04cb5..e100f27f8c38 100644
--- a/sbin/dump/main.c
+++ b/sbin/dump/main.c
@@ -168,11 +168,18 @@ main(argc, argv)
 		case 'b':		/* blocks per tape write */
 			ntrec = numarg('b', "number of blocks per write",
 			    1L, 1000L, &argc, &argv);
-			/* XXX restore is unable to restore dumps that 
-			   were created  with a blocksize larger than 32K.
-			   Possibly a bug in the scsi tape driver. */
-			if ( ntrec > 32 ) {
-				msg("please choose a blocksize <= 32\n");
+			/*
+			 * XXX
+			 * physio(9) currently slices all requests to
+			 * 64 KB chunks.  So now, if somebody entered
+			 * e.g. 96 KB block size here, he would effectively
+			 * yield one 64 KB and one 32 KB block, which
+			 * restore cannot handle.
+			 * Thus we currently enforce pyhsio(9)'s limit
+			 * here, too.
+			 */
+			if ( ntrec > 64 ) {
+				msg("please choose a blocksize <= 64\n");
 				exit(X_ABORT);
 			}
 			break;
@@ -186,6 +193,10 @@ main(argc, argv)
 			cartridge = 1;
 			break;
 
+		case 'a':		/* `auto-size', Write to EOM. */
+			unlimited = 1;
+			break;
+
 		/* dump level */
 		case '0': case '1': case '2': case '3': case '4':
 		case '5': case '6': case '7': case '8': case '9':
@@ -235,7 +246,7 @@ main(argc, argv)
 
 	if (blocksperfile)
 		blocksperfile = blocksperfile / ntrec * ntrec; /* round down */
-	else {
+	else if (!unlimited) {
 		/*
 		 * Determine how to default tape size and density
 		 *
@@ -361,7 +372,7 @@ main(argc, argv)
 		anydirskipped = mapdirs(maxino, &tapesize);
 	}
 
-	if (pipeout) {
+	if (pipeout || unlimited) {
 		tapesize += 10;	/* 10 trailer blocks */
 		msg("estimated %ld tape blocks.\n", tapesize);
 	} else {
diff --git a/sbin/dump/tape.c b/sbin/dump/tape.c
index cc7cc13c8fa2..26aed1339ff6 100644
--- a/sbin/dump/tape.c
+++ b/sbin/dump/tape.c
@@ -138,7 +138,7 @@ alloctape()
 	 * repositioning after stopping, i.e, streaming mode, where the gap is
 	 * variable, 0.30" to 0.45".  The gap is maximal when the tape stops.
 	 */
-	if (blocksperfile == 0)
+	if (blocksperfile == 0 && !unlimited)
 		tenths = writesize / density +
 		    (cartridge ? 16 : density == 625 ? 5 : 8);
 	/*
@@ -302,7 +302,7 @@ flushtape()
 	asize += tenths;
 	blockswritten += ntrec;
 	blocksthisvol += ntrec;
-	if (!pipeout && (blocksperfile ?
+	if (!pipeout && !unlimited && (blocksperfile ?
 	    (blocksthisvol >= blocksperfile) : (asize > tsize))) {
 		close_rewind();
 		startnewtape(0);