Re: MinVMS or CD backup and volume shadowing

Dale Dellutri wrote:
We have an alphaserver DS25, VMS 8.2. We're going to create a
shadow set with two data disks for the first time. My questions
are about backup/restore, specifically using MinVMS or the
mini-VMS you get by booting the VMS 8.2 Installation CD.

1. Currently we have MinVMS on DISK1 (a data disk, not a system
disk), installed via:
$ @sys$system:axpvms$pcsi_install_min DISK1
It's used as follows:
a. shutdown the system
b. boot from root SYSE on DISK1
c. make special backups (for example, a good image copy
of the system disk)
d. shutdown MinVMS and re-boot the normal system disk.
That all works fine.

Is DISK1 the system disk, or one of the data disks?

If it's a data disk, I take it you can't just quiesce
(make it close all files) or shut down the application,
and back up the data disk with online backup. If you can
do that, it would probably be much quicker than doing all
those reboots.


However, DISK1 is going to become one of the two disks in a
shadow set (assume the other disk is DISK2). I think I should
take MinVMS off DISK1 and put it on another (non-shadowed)
data disk because using MinVMS as shown above would change
DISK1 (log files in the SYSE hierarchy and so on), and when
when I re-booted, DISK1 would be inconsistent with DISK2
so that re-forming the shadow set would require some kind
of copy or merge.

Right?

I think so, since you are booting from one member of the shadow
set, but without shadowing enabled.



2. Are MinVMS or the mini-VMS system that you get by booting
the VMS 8.2 Installation CD aware of shadow sets? In other
words, when I am in the MinVMS environment, can I mount
DISK1 and DISK2 as a shadow set?


You could probably hack it so that the shadowing license
was in the LMF of the "MinVMS", along with the right settings
for the shadowing sysgen parameters, but then you wouldn't
have a quiet copy of the data disk for source of the backup
since both copies would be members of the shadow set.

However, if you only wanted to use this environment for backing
up the system disk, it would be fine.

I think you would be much better off booting from the CD or
installing the "MinVMS" environment on a 3rd disk.

Then you could mount one member of the shadow set (disk1: or
disk2:, your choice) /nowrite and back it up. Since it's
write-locked, it won't get modified, so when you reboot,
it won't do a shadow copy or merge.

Same with the system disk.

For full volume restores, you will need to mount one of DISK1
or DISK2: /foreign, then overwrite it. You could then identically
restore the other one, or (I think this would be much faster),
init the other one or mount it /override=shadow to clear the
shadowing information, then reboot. The system startup will
mount the restored disk, then you can manually add the other
disk to the set and the shadow copy will restore it. (Or you
could automate this by putting mount/copy commands in the
system startup, but that could be dangerous.) You do need to
be careful because the restored copy will be an older shadow
generation than the other disk, and shadowing will naturally
try to overwrite it by doing a shadow copy from the "newer" disk.

Advantages of the CD environment: 1) Safe from accidental changes,
2) really read-only, 3) known and static environment so there are
no suprises. (If you are doing a full-volume data or system
restore, something has gone horribly wrong and people might
be slightly panicky.)

Advantages of the "minVMS" environment: 1) You can rebuild it
any time, which will cause it to include the latest backup
and device driver ECOs, in case you have an issue with you
backups that one of the ECOs fixes, 2) you can script it with
DCL command files in it, so the operations people only need
to type "@BACKUP_SYSTEM", "@BACKUP_DATA", "@RESTORE_SYSTEM",
etc., and the command file can prompt them for tape drive
names, sanity check the disks, etc., rather than having to
type a series of non-trivial mount and backup commands. (You
could also put these command files on a disk and use them from
the CD environment, but then the ops people would have to mount
the disk and "set default" there, greatly increasing the
complexity, i.e. 3 commands vs. 1 to accomplish anything.)
3) Probably boots faster then the CD.


[Bonus question:
3. What are the official names of what I've called "MinVMS"
and "the environment you get when you boot the VMS 8.2
installation CD"? And if they don't have names, shouldn't
they?]


No idea :-)

How about Fred and Shirley? (Cue JF...)

--
John Santos
Evans Griffiths & Hart, Inc.
781-861-0670 ext 539

.

Relevant Pages

  • Re: physical drive replacement
    ... >> My first problem is determining which of the 2 physical drives in stripeset ... DELETE the disk, quiesce the bus and perform the physical swap, ... > and mount it into the shadow set, which should trigger a shadow copy ...
    (comp.os.vms)
  • Re: shadowing questions
    ... Suppose a node starts a full shadow copy on a shadow set the disks of ... Will the entire shadow set go into mount verification, picking up the copy where it was left off when the node, and the disk which is connected to it, become available again? ... The operator can then do a MOUNT from an ALPHA to enable a MINICOPY to a disk which went down with the VAX which just rebooted. ... (This works even if the shadow set has no members with a direct connection to an ALPHA.) ...
    (comp.os.vms)
  • Re: What is the Difference between Shadow and Mirrored disk?
    ... > Is a Shadow disk in OpenVMS the same as a Mirrored disk in RAID for ... A VMS shadow set is a software based solution. ... A RAID ...
    (comp.os.vms)
  • Re: MinVMS or CD backup and volume shadowing
    ... shadow set with two data disks for the first time. ... specifically using MinVMS or the ... running from a write-locked disk. ...
    (comp.os.vms)
  • MinVMS or CD backup and volume shadowing
    ... shadow set with two data disks for the first time. ... Currently we have MinVMS on DISK1 (a data disk, ...
    (comp.os.vms)