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Creating CA and BC copies

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Ninad_1
Honored Contributor

Creating CA and BC copies

Hi,

Please can anyone tell me if the below is possible.
I have a primary site with XP1024 and DR site with another XP1024. CA links are already been setup between these 2 arrays as it is used by some production applications. Now another application is planned to use storage from these arrays.
1. If I have LDEVs configured on the primary site - allocate the LUNs to VGs and create volumes and have a database using these volumes. Can I now create the CA copies for the LDEVs (at primary site) on DR site even when there is active/live data on the primary volumes. Any particular care/steps need to be followed apart from the steps to create CA copies ?
2. Once CA copies have been setup, can I now setup BC copy at primary when there is live data in the primary volumes ? Any particular care/steps need to be followed apart from the steps to create BC copies ?
3. Also can I setup BC copy for the LDEVs at DR site (required for backup copy) when there is data in the CA copies ?
4. Do I need to take outage on the CA copies to create the BC copies ? Do I need to split the link between prim and CA copies to create the BC copies at DR site ?

Please help me on this . I just want to understand how - in which sequence the above requirements need to be carried out and what are the constraints - like need to split/suspend any copies before doing anything or can do it without suspending the copies, any outages required etc, etc. so that I want to prepare a high level plan. I do not need the actual commands but need the logical steps.

Thanks a lot,
Ninad
9 REPLIES
Peter Mattei
Honored Contributor

Re: Creating CA and BC copies

Hi

All the scenarios you described above do work. See the attached pages out of the XP CV user guide describing combined BC and CA operations.

In order to get a consistent BC copy (S-vol) you need to make sure that the P-Vol is in a consistent state before splitting the BC. This is usually done by either putting the application residing on the P-vol(s) into online-backup-mode or shutting it down.
This is not an XP limitation! You need to make sure that all caches are flushed and your disks are consistent!

Cheers
XP-Pete

I love storage
Ninad_1
Honored Contributor

Re: Creating CA and BC copies

Pete,

Thanks.
Ya, I understand that all the above are possible as the same configs are used for some other applications. What I wish to know and probably not clear from my question is that for each of the steps -
Creating CA copy, creating BC copy at primary, creating BC copy at DR site - do I need to take outage while creating the copies ?

Another thing which I missed to ask was -
Currently I have an application having following config.
Prim site
One main copy, one BC copy
DR site
One CA copy of the main copy from prim, 2 BC copies (for backup and preprod)

Now there would be a application, database upgrade. For which I am proposing buying 2 extra sets of copies (one copy for prim -lets call it as COPY1 and other for DR - let call it COPY2) and using the primary BC copy after reconfiguring it as a separate copy - lets call it COPY0.

Now the COPY0 will be used for testing, COPY1 will be used for actual production migration and COPY2 will be the DR copy for COPY1. If this is the requirement will the following be possible.
1. Use the COPY0 for performing testing
2. Use COPY0 and COPY1 (with COPY0 as PVOL and COPY1 as SVOL) for testing backups using the SVOL copy
3. Destroy the BC config such that the COPY0 still has valid data, COPY1 can afford to lose data.
4. Create CA links between COPY1 and COPY2
5. Perform testing for remote failover using COPY1 and COPY2
6. Break the CA (Please let me know the correct terminology to refer to breaking the CA copies - so that the SVOL is not getting updated from PVOL)
7. Perform the live migration (To avoid slow performance during this migration - thought of breaking of CA in above step) - majority of data will be migrated here.
8. Setup CA links again, let the data get replicated and then do the differential migration - this will help in having DR copy ready at the time of live cutover with minimal affect to performance during migration.
9. After cutover, destroy the BCV copies of the original DR (as I mentioned in current config), then using COPY2 as PVOL for BC setup 2 BC copies using the space freed from destroying earlier BC copies.
10. Take backup using the newly created BC copy.
11. After a month or so (support phase) using COPY1 as PVOL create BC copy onto COPY0

Do you think this is the correct procedure and all the steps are technically possible ?Please provide your very valuable suggestions/ recommendations.

Thanks a lot.
Ninad
Peter Mattei
Honored Contributor
Solution

Re: Creating CA and BC copies

Uuh, thats a lot of questions!

Let my try to answer one question after the other:

1. To create BC or CA copies and to split them off you do not need otages if you can assure that your P-vols are consistent.

What you have to keep in mind is, that BC and CA create an exact copy of the P-vol at the time of the split.
Lets assume you have an Oracle DB residing on 10 LUNs (LDEVs) with one BC S-vol each and Oracle is running in normal mode.
If you now split the BCs off there is a chance that the image on BC is corrupt because Oracle is asynchronously writing to the LUNs and keeping some data in server cache.

Putting Oracle in online-backup-mode will flush the server cache, switch the log file and start journaling the log files. If you now split the BC vols off the result will be consistent.

Thus splitting off BC or CA S-vols can be done concurrently.

Hope that answers your first question

Peter
I love storage
Ninad_1
Honored Contributor

Re: Creating CA and BC copies

Pete,

Thanks and sorry.
Thanks because- yes my 1st question is answered.
sorry because - that a lot of questions.
Would be pleased to have your views on the steps I have mentioned and if there are any technical difficulties in doing so. - One constraint I noticed in the doc you attached in earlier reply -
"Reverse resync and quick restore operations cannot be performed on BC/ CA shared volume pairs."
Would be pleased to give points for multiple replies as lot of steps involved :)

Please advice.

Thanks,
Ninad
Peter Mattei
Honored Contributor

Re: Creating CA and BC copies

OK, will now answer your last question: "Reverse resync and quick restore operations cannot be performed on BC/ CA shared volume pairs."

Reason: These operations swap the volume map tables. This would have impact on the other relation thus it cannot work!

Read another part of the user guide talking about BC including resync and restore(attached)

Peter
I love storage
Peter Mattei
Honored Contributor

Re: Creating CA and BC copies

I tried to draw what you want to achieve. But sorry I cannot fully follow your thoughts! (its extremely difficult without drawings and chance to verbally discuss)

I suggest you call your HP salesman and ask for storage presales support.
The best would be to discuss your needs and ideas either face to face or on the phone with a storage presales representative in order to design the best possible solution for your needs!

Cheers
Peter
I love storage
Ninad_1
Honored Contributor

Re: Creating CA and BC copies

Pete,

Thanks a lot for the help.
Let me see if I can draw a few bits and explain more better.

Thanks,
Ninad
Ninad_1
Honored Contributor

Re: Creating CA and BC copies

Hi All,

I have not drawn any figure but I would like to formulate into one question -

If I have CA copies setup with CA PVOL at primary site and CA SVOL at DR site. After a while when the CA copies are used by production systems can I create
1. BC copy at primary from the CA PVOL - do I need to do anything to allow to create the BC copy when the CA PVOL is active or it simply allows ?
2. 2 BC copies at DR from the CA SVOL - do I need to do anything to allow to create the BC copy when the CA SVOL is already set for replication from the CA PVOL or it simply allows ?

Are there any risks and limitations in doing the above.
Your replies most urgently required.

Thanks a lot,
Ninad
Peter Mattei
Honored Contributor

Re: Creating CA and BC copies

You can create BC copies of CA P-Vol and S-Vol at any time, no restrictions!
The BC copies will be a 100% copies of all data residing on the source volume!

Cheers
Peter
I love storage