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Volume Shadowing and minicopy

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Rob Crooks
Frequent Advisor

Volume Shadowing and minicopy

After some great help, I have a DS20 booting from a shadowed system disk across 2 MSA1000's.
I have created and Shadowed 2 additional virtual drives by mounting them with the /policy=minicopy switch and now I realize that I should have
mounted the system disk with the same switch.

My question is if I can now go back and re-mount DSA0 (system disk) with minicopy to take advantage of the reduced sync time opon rebuild.

I guess I could leave the system as-is, but from what I have read, it has real advantages in disaster recovery.

Thanks
2 REPLIES
John Gillings
Honored Contributor
Solution

Re: Volume Shadowing and minicopy

Robert,

You can remove one of your physical units and mount it back with:

$ MOUNT/CLUSTER DSA0/SHADOW=removed-unit/POLICY=MINICOPY=OPTIONAL volume-label

This will result in a full copy, but it leaves the shadow set with mini copy enabled. Next time:

$ DISMOUNT/POLICY=MINICOPY physical unit

then

$ MOUNT/CLUSTER DSA0/SHADOW=removed-unit/POLICY=MINICOPY volume-label

The member will be minicopied rather than a full copy.

One caveat here... if this is a system disk, most of the data is static readonly, and available on distribution CDs, so you really don't need to remove a member from a shadowset to back it up (that's if you think you need to back it up at all!). The changing data on the system disk, SYSUAF, RIGHTSLIST etc... tend to be open files, so removing a shadow member DOES NOT guarantee a consistent copy of these files.

So, what you get you don't need, and what you need you don't get. Doesn't sound like a good plan to me!

Please review your reasons for wanting miniCOPY on your system disk! And review your backup strategy. See OpenVMS Technical Journal Volume 1 for a discussion of backup strategies for system disks.

>I guess I could leave the system as-is,
>but from what I have read, it has real
>advantages in disaster recovery.

MiniCOPY doesn't help much in disaster recovery as it only does anything if volumes are explicitly DISMOUNTed.

On the other hand miniMERGE (HBMM) is VERY useful in recovery and would be a very worthwhile thing to have on a system disk. See:

$ SET SHADOW/POLICY=HBMM=(etc...)
$ SET SHADOW/ENABLE=HBMM
A crucible of informative mistakes
Rob Crooks
Frequent Advisor

Re: Volume Shadowing and minicopy

Thank you very much for the insite. I guess I will look again at what I want, from what you said I am not going to get what I want using minicopy.

Much appreciated.