[Info-vax] Sizing up Disks with Shadowing

[Ken Fairfield]

On Aug 11, 1:07 pm, Tom Adams <tadams... at yahoo.com> wrote:
[...snip...]
>
> My shadow set is my system disk.  So I guess I would have to
> use the /limit command when booted off the CD.

This might me a good time to go visit the FM!  In truth, I've
never tried this with a system disk, but the online help doesn't
make any distinction between systems disks and "normal"
disks.  Caveat emptor...

> You use the /LIMIT command on the disk when its not in the shadow
> set.  But I thought you said it was overwritten.  I guess its only
> overwritten if the member is being added to a shadow set?  the /limit
> is not overwritten if its on the volume used to first form the shadow
> set.

To create a shadow set[*], you first need to do a "normal" initialize
on some disk, then mount that disk /Shadow, then shadow copy
additional member(s).

[*] Recent versions of VMS include INITIALIZE/SHADOW so that
a multi-member shadow set can be mounted without shadow copy
immediately after initialization.  But see the various caveats when
doing so...

So the first member keeps its volume initialization parameters while
additional members become exact copies of the first...including the
volume parameters.  How you initialize the disks being shadow copied
doesn't matter.  They get overwritten.

It's just that you can't do the mount/shadow of a "raw" out of the
package, uninitialized disk.  You need some VMS volume structure
defined on it before you can add it to the shadow set.  But that can
be very minimal, as I showed before.

Back to your system disk shadow set...  What you might do is:

1) Shadow copy in the big disk.
2) When the copy completes, dismount the big disk.
3) Mount/Override=Shadow, private, the big disk.
4) Show Device/Full on the big disk and note the
    "Total Blocks", "Logical Volume Size" and the
    "Expansion Size Limit".
5) Do a Set Volume/Limit on the big disk.
6) If the Expansion Size Limit hasn't changed,
    dismount and remount the disk, and verify
    the limit has changed.
7) Do a Set Volume/Size on the big disk.  Again
    verify the Total Blocks and Logical Volume Size
    have changed.  If not, dismount and remount
    to confirm.
8) Shut the system down, change the console
    parameters to boot the big disk.  Then boot
    the big disk as the new system disk.
9) Shadow copy in any additional system disk
    shadow members.

If you're not confident that you'll have a good/pristine
copy of the system disk when you split off the big
member, then go ahead and do the /LIMIT stuff
with the system booted from the CD as you suggested.
If yours is not a busy system, e.g., a hobbiest system,
splitting the shadow set will probably be fine.

The other way to do this would be to initialize the
big disk with /LIMIT, the do an /IMAGE backup
from the system disk to the big disk with /NOINIT
on the BACKUP command.  Then proceed to shut
down and boot off the big disk.

In another follow-up, you write:
> These disks were probably initialize way back on an earlier version of
> VMS.  I wonder if that will make a difference?

I don't know, but I don't think so.  I think the
SET VOLUME/LIMIT does all the reorganization
that's needed.  (Does anyone know if it recreates
BITMAP.SYS or some such?)

    -Ken