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Splitting and resynchronising BC/CA pairs

Ninad_1
Honored Contributor

Splitting and resynchronising BC/CA pairs

Hi,

If I have BC or CA pairs configured - such that at primary site I have one primary copy and a BC copy and the remote site has the CA copy and following are things I wish to perform. Please suggest what I need to do - like split/suspend BC/CA copies ? , resynchronise - can start full copy.
1. I want to perform some testing which will do a lot of data changes on the primary copy of the BC or CA , but I do not want the changes to be replicated to the BC/CA pairs as I am just doing some testing and so not need the data to be replicated.
2. Now after the testing is complete I again want to sync the data to CA copy but still do not want the BC copy to get replicated
3. Finally I want the BC copy to be updated with the data on primary copy.

One more doubt I have is if a BC/CA pair is split or suspended for how long the shared memory will track the data changes - say if I have 512 MB shared memory - or on what will ot depend. And say once the shared memory is full what happens ? Is it required to perform a full data copy ? what are the operations involved - when do I suspend, when do I split and when do I delete BC and CA copies ?

Thanks a lot,
Ninad
3 REPLIES
Ivan Ferreira
Honored Contributor

Re: Splitting and resynchronising BC/CA pairs

You can break the copy set in continuous access. From there, you will have independent disks and can be used as you want. After you did your test or changes at the source eva, to re-sync the data, you must delete the destination vdisk, create a new copy set and wait for a full copy.

You can also suspend, do the changes, and then resume, but there is a problem. If you must use the disk which has the old data, you cannot do a "failover" if the DR Group is suspended, you must take offline the source storage to allow this and resume the DR Group, so is better if you break the copy set instead of suspend it.

Data changes will be stored on a log disk as long as you have enough free space on your disk group, after that, the copy set is marked for a full copy.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Ninad_1
Honored Contributor

Re: Splitting and resynchronising BC/CA pairs

Ivan,

Thanks for your inputs. Need some clarification. Sorry I forgot to mention that I have XP1024 arrays.
So you said that I can either break the copy - What term is used for this - is it split or delete ?
or I can suspend the CA copy - the only limitation is I cannot use the DR copy - thats not a problem, I am just doing the testing prior to production. But after I resume or rather resync - Will the CA software automatically decide whether it needs a full copy (if changes have overflowed the shared memory) or update copy ?
Also Please can you provide the steps I need to follow for each of the step in my question.

Thanks a lot,
Ninad
Nigel Poulton
Respected Contributor

Re: Splitting and resynchronising BC/CA pairs

Hi Ninad,

Not sure if you still need an answer to this so I wont spend much time on an answer in case your already sorted.

The cache related question obviously depends on how much shared memory you have and how many wirtes are going to your P-VOL while the pairs are "split". Deleted pairs do not have changes to the P-VOL and S-VOL tracked in SM.

If you have too many writes and this fills up the differential bitmap in your SM it is said to puncture your SM and you lose the track map making a full copy required.

They have fixed this with the XP12000 CA journal mode where changes are tracked to journal volumes (disk) and not SM.
Talk about the XP and EVA @ http://blog.nigelpoulton.com