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July 18th, 2014 04:00
Need help with deletepair in SRDF/A
Please provide information regarding deletepair in SRDF/A.
I need to delete few device pairs from a running RDF group.
I have read few discussions on the same in ECN and have found two ways of doing it and am not sure which one is most appropriate?
1st Method: Create a new RDF group with the -f containing the devices to be removed and then do a movepair from the running RDF group to the new RDF group. Later do, suspend and deletepair with the new RDF group.
Or
2nd Method: Just have two files with one file containing the devices to be removed and the second file having the devices which need to continue to stay. Then perform suspend and deletepair on the file containing the devices to be removed. At the end, just to ensure that consistency is maintained on the devices which need to stay, perform set mode async and enable consistency on them.
In this second scenario, all these operations have the same RDF group all the time. Does this not affect the RDF group in any way?
Also, the command just prior to deletepair, should be suspend or set mode acp_disk
PedalHarder
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July 22nd, 2014 15:00
Just suspend and movepair. The delete/createpair operations are carried out in the maintenance RDFG.
1. No, it can be done in the SRDF/A RDFG, but i am proposing that it it is done in the maintenance RDFG.
2.If you are using a maintenance RDFG, the suspend/movepair is done on the SRDF/A RDFG and the deletepair is done in the maintenance RDFG.
3. The suspend /deletepair does not affect the consistency of the devices running in SRDF/A mode. Certain query commands can show an overall inconsistent state for the SRDF/A RDFG though. This is another reason to use the maintenance group as it minimises the time the RDFG is reported as inconsistent due to device maintenance activities.
4. Deletepair should not need cons_exempt as it is already in that state from the suspend.
5. Suspend is fine. The device should have stopped being used prior to this work and as a result of the suspend, no invalid tracks should build up due to host writes to the R1 device.
Symm_Unlimited
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July 18th, 2014 04:00
In the above query, there is a correction to avoid any confusion. In the sentence:
"1st Method: Create a new RDF group with the -f containing the devices to be removed"
"with" should be "and", so the correct sentence is:
"1st Method: Create a new RDF group and the -f containing the devices to be removed"
Symm_Unlimited
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July 18th, 2014 05:00
In both the methods, the suspend has been done using the -cons_exempt.
Also, if possible, please post the Symmetrix procedure generator output for SRDF/A deletepair
PedalHarder
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July 20th, 2014 17:00
I prefer the maintenance RDF group method for all maintenance activities in and out of the active SRDF/A group. The create-pair, and initial synch is done outside the active SRDF/A session and only moved into the group when the synch is performed. The same in reverse... Apart from the suspend and move-pair, maintenance tasks are carried out outside the active SRDF/A session. I think this is safer because there is no messing with the active SRDF/A session except suspend and movepair.
Symm_Unlimited
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July 22nd, 2014 00:00
Hi Jason,
Thank you for the reply.
I could not understand this sentence above: "Apart from the suspend and movepair, maintenance tasks are carried out outside the active SRDF/A session."
Do you mean that: Apart from suspend, movepair "and deletepair", maintenance tasks are carried out outside the active SRDF/A session.
I have few doubts which are mentioned below. I request you to please reply with a Yes or No for most of them, which will clarify those doubts.
Considering the scenario only for deletepair in SRDF/A with 5874 onwards
R= filename for the file containing the device pairs which need to be removed from the active SRDF/A session
1.) To perform SRDF/A deletepair, do we need to create a new RDF group? (Yes/No)
2.) On the file R (mentioned above), are the suspend and deletepair performed on the "active SRDF/A RDF group"? (Yes/No)
1.) and 2.) are quite similar.
3.) Does performing suspend and deletepair on the active RDF group, affect its consistency? (Yes/No)
3.) i.) If yes, what is the procedure to restore the active RDF group's consistency?
4.) Like the suspend command on the active RDF group is issued with -cons_exempt, does the deletepair on the active RDF group command also need -cons_exempt? (Yes/No)
5.) Which is the correct command to be used just prior to deletepair, is it "suspend" or "set mode acp_disk"?
sauravrohilla
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July 22nd, 2014 20:00
I kind of agree to Jason's suggestion of keeping the procedure simple, disable consistency, suspend SRDF/A and use movepair commands to move the devicepair from/to the target RDFG.
It does not mean that the steps that you want to perform (using the cons exempt) is not good but it jst adds to the complicity
If you have quite a large RA group with 100 of device pairs then your procedure seems appropriate but with fairly small set of devicepairs, i would go with Jasonc 's plan
regards,
Saurabh