SUMMARY: Taking part of a disk out of Veritas

Hi,

Thanks for all who replied. There seems to be no consensus on this issue, I got an equal amount of replies saying "it's not possible" and "yes, this is the way to do it". Since as of writing this I have not had the time to actually try and follow the suggested procedures and see the result, I quote here both types of replies.

Here follows the original posting and the replies that I got (in order of appearance :-)).

Ors

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Original posting:

> I have a Netra T1405 with 1G of RAM running Solaris 8 and 
> VxVM. The root disk is encapsulated, the rest of the disks 
> are also under Veritas control, in two disk groups. Since 
> much of the available literature advises against having the 
> dump device on a disk controlled by Veritas, I thought of 
> setting it up on a portion of disk which is not under Veritas 
> control (unfortunatelly installing one more disk is not an option).
> The question is: is it possible to take a part of one of the 
> disks out of Veritas, so that it becomes accessible by its 
> "conventional" Unix device? In all the setups that I have 
> seen so far Veritas controlled the entire disk, eg. c0t0d0s2. 
> Is this doable, and if so, how?

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Alan Pae:

Vertitas is all or nothing, either it controls the disk or it does not

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Michael Maciolek:

This page gives instructions on how to make part of a disk available
to Veritas.  Although the instructions are intended for a different
final goal - creating a small rootdg - they should allow you do do
what you need as well.

	http://www.carumba.com/talk/veritas/singleslicerootdg.shtml

It looks as though you will need to take one disk completely out of
Veritas, partition it, and then return just a piece of it to Veritas.


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Paulo Fessel:

It's possible to do this - here we set up rootdg in one slice of each disk we have under Solstice DiskSuite control.

However, if I understood you allright, you'll have to vxevac one of the disks to take it off the DG and make it available again to Solaris. After this has been done, use one of the slices to do your memory dump (1 GB partition as you're using 1 GB RAM, right?).

Then, use the remaining space of the disk as a single slice and make it available again to Veritas. 

In short:

1. /etc/vx/bin/vxevac -g dgname diskname
2. format
3. select <diskname>
4. create slices - 1 for dump, 1 for Veritas
5. add the Veritas slice back to the DG:
   # vxdctl add disk <diskname> type=simple (ignore WARNING - the disk is added to /etc/vx/volboot)
   # vxdisk -f init <diskname> type=simple (initializes disk)
   # vxdg -g dgname adddisk <diskname> (adds to dgname)
   # vxdctl enable (activates all modifications)


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Gary Chambers:

VxVM requires exclusive use of any devices under its control.  Have you
considered using Solstice DiskSuite for mirroring the root filesystem?

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Pascal Grostabussiat:

As far as I know this is not possible. When Veritas take over a disk it
overwrites the label of the disk (eventually moves the boot-block if
necessary to not loose it in case of encapsulation). There is no better
granularity than disk-wise.

Another point, the only reason for encapsulating the boot-disks is
to mirror them. But encapsulating the boot-disks increases complexity.
 From my own experience, encapsulating the boot-disks with Veritas is
some kind of "religion", you feel you have to do it or not. Here in
Sweden the religion seems to be "encapsulate" (maybe because Veritas
tells people to do it). In other european contries the religion is "no
encapsulation" because not necessary and provides higher complexity.

If you want to mirror the boot-disks, you could still use Solstice
DiskSuite and mirror partitions/slices but not whole disks so that you
could still have one or a few partitions on their own. But whatever you
use the partitions/slices for, think about possible performance issues.
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