diff --git a/sbin/mdmfs/mdmfs.8 b/sbin/mdmfs/mdmfs.8
index 1259309e7752..7b9e810683d3 100644
--- a/sbin/mdmfs/mdmfs.8
+++ b/sbin/mdmfs/mdmfs.8
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd November 3, 2006
+.Dd February 15, 2007
 .Dt MDMFS 8
 .Os
 .Sh NAME
@@ -39,8 +39,8 @@ driver
 .Op Fl DLlMNPSUX
 .Op Fl a Ar maxcontig
 .Op Fl b Ar block-size
-.Op Fl c Ar cylinders
-.Op Fl d Ar rotdelay
+.Op Fl c Ar blocks-per-cylinder-group
+.Op Fl d Ar max-extent-size 
 .Op Fl E Ar path-mdconfig
 .Op Fl e Ar maxbpg
 .Op Fl F Ar file
@@ -114,19 +114,18 @@ out before forcing a rotational delay
 option).
 .It Fl b Ar block-size
 The block size of the file system, in bytes.
-.It Fl c Ar cylinders
-The number of cylinders per cylinder group in the file system.
+.It Fl c Ar blocks-per-cylinder-group
+The number of blocks per cylinder group in the file system.
 .It Fl D
 If not using auto-unit,
 do not run
 .Xr mdconfig 8
 to try to detach the unit before attaching it.
-.It Fl d Ar rotdelay
-Specify the minimum time in milliseconds required to initiate another
-disk transfer on the same cylinder.
-Modern disks with read/write-behind achieve higher performance without
-this feature,
-so it is best to leave it at 0 milliseconds.
+.It Fl d Ar max-extent-size
+The file system may choose to store large files using extents.
+This parameter specifies the largest extent size that may be
+used.  It is presently limited to its default value which is 16
+times the file system blocksize.
 .It Fl E Ar path-mdconfig
 Use
 .Ar path-mdconfig
diff --git a/sbin/mdmfs/mdmfs.c b/sbin/mdmfs/mdmfs.c
index 5b895d5ddbf7..c552f567ced0 100644
--- a/sbin/mdmfs/mdmfs.c
+++ b/sbin/mdmfs/mdmfs.c
@@ -656,10 +656,11 @@ usage(void)
 {
 
 	fprintf(stderr,
-"usage: %s [-DLlMNPSUX] [-a maxcontig] [-b block-size] [-c cylinders]\n"
-"\t[-d rotdelay] [-E path-mdconfig] [-e maxbpg] [-F file] [-f frag-size]\n"
-"\t[-i bytes] [-m percent-free] [-n rotational-positions] [-O optimization]\n"
-"\t[-o mount-options] [-p permissions] [-s size] [-v version]\n"
-"\t[-w user:group] md-device mount-point\n", getprogname());
+"usage: %s [-DLlMNPSUX] [-a maxcontig] [-b block-size]\n"
+"\t[-c blocks-per-cylinder-group][-d max-extent-size] [-E path-mdconfig]\n"
+"\t[-e maxbpg] [-F file] [-f frag-size] [-i bytes] [-m percent-free]\n"
+"\t[-n rotational-positions] [-O optimization] [-o mount-options]\n"
+"\t[-p permissions] [-s size] [-v version] [-w user:group]\n"
+"\tmd-device mount-point\n", getprogname());
 	exit(1);
 }