SUMMARY: Metadisk Mirror re-sync

From: Roetman, Paul <>
Date: Thu Jan 08 2004 - 22:16:00 EST
Original question about re-syncing Metadisks below...

Thanks to 
  Darren Dunham
  Julie Baumler
  David B. Harrington
  Ellen Davis 
  and anyone else who spent time on this!

Darren came up with the solution first!...and there were some close variants
of that solution!

Some interesting reading on booting from different mirrors

Here is the final method:

Disk layout
  d0 = default boot disk (root partition)
  d10 = sub mirror one
  d20 = sub mirror two.

1.	Confirm standard boot device d0, with sub-mirrors of d10 and d20

2.	determine physical devices
        metastat d10  --> /dev/dsk/c0t1d0s0
        metastat d20  --> /dev/dsk/c0t0d0s0

3.	determine physical address of device
        ls -l /dev/rdsk/c0t1d0s0 -->
        ls -l /dev/rdsk/c0t0d0s0 -->

4.	setup boot names at "ok" prompt
        nvalias bootdisk
        nvalias mirrdisk

5.	Break mirror and setup each boot disk
        metadetach d0 d20
        touch /d0.disk                     (create dummy file to verify disk
        mount /dev/md/dsk/d20 /usr/dummy   (mount into a dummy directory)
        cd /usr/dummy
        metaroot  -n /dev/md/dsk/d20       (obtain what changes are
        edit vfstab, set root disk to d20  (get all this info from metaroot
        edit system, modify to this 
        touch /usr/dummy/d20.disk

6.	Confirm boot off each disk, verify dummy file
        boot bootdisk
          verify /d0.disk exists
        boot mirrdisk
          verify /d20.disk exists

At this point, can apply patches to d0 or make config changes to d0 - with a
good backup of original system on d20. 

7.	If all goes well with patches the copy changes from d10 to d20
        boot bootdisk
        confirm /d0.disk exists
        metattach d0 d20
        metastat d0                    (to confirm sync complete)
        confirm /d0.disk exists

8.	If patch application/config changes FAIL, copy d20 to d10
        boot mirrdisk
        verify /d20.disk exists
        mount /dev/md/dsk/d0 /usr/dummy    (not really necessary)
        verify /usr/dummy/d0.disk exists
        umount /usr/dummy

        metaclear d0                   (remove old d0 .. d10 does not
        metainit  -f d0 -m d20         (force creation of d0 to d20 mirror)
        metaroot  -n /dev/md/dsk/d0    (print what todo without doing it)
        metaroot  /dev/md/dsk/d0       (actually run the command)
        reboot                         (boots off default of d0)
        metattach d0 d10
        watch re-sync!


Another solution suggested was

I haven't had a chance to test it, but in theory, it looks like you can
(unsupported) edit /etc/lvm/ to tell it that d0 is made up of d20 with
d10 as a mirror.  

/etc/lvm/md.conf should initially have said something like:

d0 -m d10 d20 1
d10 1 1 c0t0d0s0
d20 1 1 c1t0d0s0

But after the metadetatch says something like:

d0 -m d10 1
d10 1 1 c0t0d0s0
d20 1 1 c1t0d0s0

Edit it to:

d0 -m d20 d10 1
d20 1 1 c1t0d0s0
d10 1 1 c0t0d0s0


There doesn't seem to be a real win in this process over the other though;
the only place I could possibly see it as being useful is with live upgrade
where you can't run meta* commands on your inactive boot environment but may
wish to only do one reboot to change BE's and fix your disk setup - even in
that case, I suspect you really should be using etc/lvm/ which IS



There may be a simple solution for this, but I cannot see it (or it's just
been a long day!!).... 

If I have the metadisk setup for the root disk 
  d0 mirror to d10 
  d0 mirror to d20 

If I detach d20 
  metadetach d0 d20 

I can then boot of either d0 or d20 (have tested this). There are great
examples on this from BigAdmin in 817-0407-10.pdf - Configuring Boot Disks
With Solaris(tm) Volume Manager Software

If I boot of d0, then I can re-attach and sync d20 (i.e. d20 is a copy of
d10), this is no problem...BUT, it I boot on d20 (and make changes to d20)
is there a simple way to sync d0 (or d10) to d20, so d10 is then an exact
copy of d20.

The only way I can see so far is to completely destroy d0 and d10, then
rebuild the whole mirror...this seems a bit over the top!


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Received on Thu Jan 8 22:15:55 2004

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