--- mdadm.8.old	Tue Feb 10 19:19:00 2004
+++ mdadm.8	Tue Feb 10 19:44:18 2004
@@ -363,7 +363,16 @@
 .TP
 .BR -a ", " --add
 '''add, or
-hotadd listed devices.
+hotadd listed devices as spare disks. 
+
+To add active disks to an array, you will need to recreate the array. If it is
+RAID1, you can often get away with recreating the array using the same
+devices, plus one more, without destroying data (creating a RAID1 device only
+overwrites the superblock).  Note that backing up the array to a regular file
+system on your new disk first is strongly recommended, but if all goes well,
+you should not have to recopy any more data. For RAID0 and RAID5, adding
+active disks will require a raid-tools 1.0 utility called raidreconf. Please
+be aware that there are risks involved with these tools, and plan accordingly.
 
 .TP
 .BR -r ", " --remove