SUMMARY: Patching with SVM mirroring boot drives

Thank you to the following people for replying to my question. (See original
question below.)

Santhosh Valarani
Mehran Salehi
Hike
Musa Williams
Kim DeSmaele

and especially Roberto Fratelli who provided me with the most detailed
explanation.

Original Question:

"I'm getting ready to patch some Solaris boxes with Recommended patch
clusters. The boot drives are using SVM in a mirror configuration. What I
would like to do is metadetach one of each of the mirrors submirrors out of
the configuration so if something goes wrong with the patching, I could boot
off of the detached submirrors and then resync the other disks back into a
configuration. Is this or something like this possible with SVM?"

The answers I received were a resounding "Yes, you can do it." But here are
the general instructions that Roberto Fratelli provided that I will be
working off of.

Here's an example :

/dev/md/dsk/d10 > / filesystem
/dev/md/dsk/d20 > /var filesystem
/dev/md/dsk/d50 > swap

The output of 'metastat -p' :

d50 -m d51 d52 1
d51 1 1 c1t0d0s1
d52 1 1 c1t1d0s1
d20 -m d21 d22 1
d21 1 1 c1t0d0s5
d22 1 1 c1t1d0s5
d10 -m d11 d12 1
d11 1 1 c1t0d0s0
d12 1 1 c1t1d0s0


use 'prtconf -vp | grep bootpath' to find out which
disk you booted off from. In my case, it was from
/dev/dsk/c1t0d0. So we will need to detach the
metadevices from c1t1d0.

- Detaching the mirrors :

# metadetach d10 d12
# metadetach d20 d22
# metadetach d50 d52

- Mounting the root filesystem from your mirror :

# mount /dev/dsk/c1t1d0s0 /mnt

- Edit /etc/vfstab entries to point to the disk
slices, not the svm metadevices ( let's say, instead
of /dev/md/dsk/d10 you put /dev/dsk/c1t1d0s0 ).

- Edit /etc/system and comment out ( using an asterisk
* ) the line starting with " rootdev:/pseudo/md "

- Put your system in OBP and boot from the mirror disk
( on this example, c1t1d0 )

- Check if your system booted fine. If yes, bring it
back to OBP and perform a normal boot ( from your
regular boot disk) and do the OS patching.

If you run in trouble with your recently patched OS,
you can boot from your mirror.

To continue off where Roberto left, if all goes well you can just metattach
the devices back into the mirror and let them resync or if all doesn't go
well you can boot off of the un-mirrored drives and recreate the SVM mirror
configuration so the "other" sync off of your good drives.

Thank you again,
--
Romeo Theriault
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