[Veritas-vx] 1+0 how to detach?

[Darren Dunham]

> 
> You can use simple vxprint -ht to find out plexes
> though vxprint -hrt also gives detailed information. 
> Here is the procedure (not tested, found on net only)
> to detach a plex for the backup 
> 
> 1. Disassociate one of the mirrors from the volume to
> be backed up:
> 	vxplex dis <plex name>
> 2. Create a new, temporary volume using the
> disassociated plex:
> 	vxmake -g <disk group> -U gen vol tempvol plex=<plex
> name>

That doesn't work for "striped-pro" or "1+0" volumes.  Instead of a nice
plex that represents the whole volume, you have separate plexes for each
section of the stripe rather than the volume as a whole.

Probably the easiest way to do it is to "convert" the volume to a normal
or "0+1" stripe before breaking off the mirror.  It only takes a second
or two to complete.

vxassist convert <volume> layout=mirror-stripe

Now you've got a "normal" set of mirrored stripes where you can break
one of the mirrors off.

> 3. Start the new volume:
> 	vxvol start tempvol
> 4. Clean the new volume before mounting:
> 	fsck -y /dev/vx/rdsk/<disk group>/tempvol
> 5. Mount the new volume and perform the backup
> 6. Unmount the new volume
> 7. Stop the new volume:
> 	vxvol stop tempvol
> 8. Disassociate the plex from the new volume:
> 	vxplex dis <plex name>
> 9. Reattach the plex to the original volume:
> 	vxplex att <volume> <plex name>
> 10. Delete the temporary volume:
> 	vxedit rm tempvol

And when you're ready to put everything back in place, just convert it
back to 1+0 with

vxassist convert <volume> layout=stripe-mirror

Note that unless you have fast resync of some sort licensed, the mirror
reattach will be a full resync of every block, even if it is only
detached momentarily.

-- 
Darren Dunham                                           ddunham@taos.com
Unix System Administrator                    Taos - The SysAdmin Company
Got some Dr Pepper?                           San Francisco, CA bay area
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