upon reboot you get the following errors

Boot device: 2.6  File and args: 
SunOS Release 5.5.1 Version Generic_103640-08 [UNIX(R) System V Release 4.0]
Copyright (c) 1983-1996, Sun Microsystems, Inc.
VxVM starting in boot mode...
configuring network interfaces: hme0.
Hostname: b01b
vxvm: NOTE: Setting partition /dev/dsk/c1t2d0s1 as the dump device.
VxVM starting special volumes ( swapvol )...
RDAC driver loaded
Segmentation Fault - core dumped  <------problem here !!!
RDAC daemons initiated
Waiting for full RDAC initialization ...
VxVM general startup...
The system is coming up.  Please wait.
checking ufs filesystems
/dev/vx/rdsk/datadg/vol01: No such file or directory
Can't stat /dev/vx/rdsk/datadg/vol01
/dev/vx/rdsk/datadg/vol01: CAN'T CHECK FILE SYSTEM.
/dev/vx/rdsk/datadg/vol01: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.

WARNING - Unable to repair one or more of the following filesystem(s):
         /dev/vx/rdsk/datadg/vol01
Run fsck manually (fsck filesystem...).
Exit the shell when done to continue the boot process.


Type Ctrl-d to proceed with normal startup,
(or give root password for system maintenance): 
Entering System Maintenance Mode

this is caused when /etc/rcS.d/S45rdac tries to start /usr/lib/osa/bin/rdaemon
it core dumps, and no devices on the sonoma(s) are seen :-(      

I trussed the /usr/lib/osa/bin/rdaemon to see why it coredumps
here are the last few lines

678:	stat("/etc/raid/rmparams", 0x0006F988)		= 0
678:	stat("/etc/raid/rmparams", 0x0006F988)		= 0
678:	open("/etc/osa/rm6mnf", O_RDONLY)		= 3
678:	open("/etc/raid/locks/rm6mnf.lock", O_RDWR|O_CREAT, 0600) = 4
678:	fcntl(4, F_SETLKW, 0xEFFFF398)			= 0
678:	fstat(3, 0xEFFFF2D8)				= 0
678:	ioctl(3, TCGETA, 0xEFFFF264)			Err#25 ENOTTY
678:	read(3, " R A I D   M o d u l e  ".., 8192)	= 49
678:	read(3, 0x000A3564, 8192)			= 0
678:	    Incurred fault #6, FLTBOUNDS  %pc = 0x0001DD3C
678:	      siginfo: SIGSEGV SEGV_MAPERR addr=0x00000000
678:	    Received signal #11, SIGSEGV [default]
678:	      siginfo: SIGSEGV SEGV_MAPERR addr=0x00000000
678:		*** process killed ***


it seems that the file /etc/osa/rm6mnf had been corrupted and 
was causing rdaemon to coredump, I moved the file /etc/osa/rm6mnf
out of the way and rebooted, rdaemon recreated this file and I
could access all the devices on the sonoma(s)

the corrupted file looked like this:
RAID Module 01~1T63350899~~1T63350926~ 1~0

the new /etc/osa/rm6mnf re-created by rdaemon looked like this:
RAID Module 01~1T63350899~ 0 2 3~1T63350926~ 1~0