SUMMARY: boot from mirror

Hi all,
  I am able to solve the "booting from mirror" problem. I would like to 
thank: 

Steve Beuttel <scb1@erols.com>
Chris L. Anderson <CA07@ridemetro.org>
Harrington, David B. (Contractor) (DSCR) <David.Harrington@dla.mil>
Parkins, Larye (NIH/NIAID) <LParkins@niaid.nih.gov>
Jem Richards <jrichards@aami.com.au>
Cris Lovett <cris@clcuk.demon.co.uk>

for their prompt responces and valuable suggestions. My original
question was:

I have a Ultra Enterprise 2 system running Solaris 8. It has 2
internal disks of 2.1 GB. I sliced the disks into 3 for storing database
replicas, / and swap. I created 2 sets of database replicas on both the
disks. I created meta devices to mirror / and swap and they also got
synced. But the whole idea behind doing this is to make sure that if the
primary disk fails, then the secondary disk will take its place. For
example, if there is power failure and the primary disk fails, the
system should be able to boot from the secondary disk. I tried to boot
from the secondary by removing the primary, but the system shows me lot
of errors like "no write permission on the meta device", "no read
permission" etc. It prompted me to fsck the meta device and I did the
same. But it keeps prompting me to do the same thing again and again. It
also says that 2 database replicas on the secondary are not enough,
though the docs say that 2 should be good enough. So, I am wondering
whether it is possible for a system to boot from either disk at any
time, whether 2 database replicas on each of the 2 disks is enough? If
possible, to what device the "boot-device" should point to 1) disk0
(primary), 2) disk1 (secondary), 3) the root slice of disk1 where / is
stored. How can I change the what "boot-device" should point to? Please
give me any pointers or suggestions. Thanks a bunch! I will surely
summarize.

And the solution for the above problems are, one should make sure that
the / mirrors are bootable. Once can use the command:

# installboot /usr/platform/`uname -i`/lib/fs/ufs/bootblk
/dev/rdsk/c0t8d0s0

to make the / mirrors bootable. The following document will be a lot
useful: http://www.sunhelpdesk.com/users/john/002.htm 

Next, one should let the system know that it can try to boot from the
primary or secondary disks which ever is first available by using the
following command at the 'ok' prompt:

setenv boot-device disk0 disk1

where disk0 is the primary and disk1 is the secondary. That way even if
one disk fails, the system can boot from the other disk. Remember that
we may need to make the secondary bootable by using the command
'installboot'. Now the system can boot from any disk, but the problem
now will be that if one disk fails, only half the database replicas will
be available, and the system complains about insufficent database
replicas, write permissions, read permissions etc. To over come this
problem modify the file /etc/system by appending the line:

set md:mirrored_root_flag=1

That way, it will allow the system to boot even if just half the
database replicas are available, but it is valid only in Disk Suite
4.2.1 which comes with the solaris 8 OS. This has been suggested by both
Steve Beuttel and Jem Richards. Thanks a lot again!

regards,
Aravind
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