I have been able to wirk around the problem with reselects not working 
properly with two or more disks active at a time. I used to get a lot of 
"RESELECT: 7 bytes in FIFO" when accessing two drives at the same time, 
so I disabled reselects in the sys/arch/sparc/dev/esp.c by applying the 
following patch.

--- esp.c.ORIG	Fri Mar 15 09:23:56 1996
+++ esp.c	Fri Mar 15 09:25:05 1996
@@ -574,5 +574,5 @@
 	 * happy for it to disconnect etc.
 	 */
-	ESP_WRITE_REG(sc, ESP_FIFO, MSG_IDENTIFY(lun, 1));
+	ESP_WRITE_REG(sc, ESP_FIFO, MSG_IDENTIFY(lun, 0));
 
 	if (ti->flags & T_NEGOTIATE) {
------------------------
After this all three drives seem to work, although somewhat more slowly 
than usual as thay cannot be accessed simultaneously. Since only one disk 
is used for most programs this is at least workable for now. 

I don't have the knowledge needed to debug the esp driver myself, but I 
will happily assist in testing and otherwise attempting to locate the 
problem.

Peter