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148 Posts
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6596
SRDF help needed
Hi All,
I am planning to move few devices from 1 srdf group to the other.Currently all devices are in async mode and in consistent state.
I tried to execute the below command after splitting up the replication.(devices are in split status now)
symrdf -sid 4757 -rdfg 3 -file rdf.txt movepair -new_rdfg 4
But I am getting the below error:
The device does not have a valid RDF Consistency state for this operation
I found writes are happedning to the R1 devices.I tried to delete the pair also.getting same error.Any suggestion to resolve this issue.
Thanks in Advance.
John Toner
61 Posts
0
September 19th, 2011 08:00
Try a 'symrdf -sid 4757 -rdfg 3 -file rdf.txt disable' command first, then re-try your commands.
John Toner
61 Posts
0
September 19th, 2011 09:00
No. This just disables the consistency protection for the SRDF/A pairs.
Consistency protection is used for SRDF/A devices. When enabled, if a single R1 device in the RA group is unable to send its data to the R2, it drops entire group so it maintains a consistency copy on the R2 side.
To re-enable consistency protection, you would just issue the 'symrdf enable' command once your movepair operation is completed.
anoopcr
148 Posts
0
September 19th, 2011 09:00
If I issue symrdf -sid 4757 -rdfg 3 -file rdf.txt disable, will it create any production issue ?
anoopcr
148 Posts
0
September 19th, 2011 10:00
Hi John,
It worked.Thanks for your help.
sauravrohilla
859 Posts
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September 19th, 2011 10:00
Alternatively, you can use cons_exempt flag while doing the move pair or the deletepair on the consistency enabled ra group.
dkakljkml
29 Posts
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June 28th, 2013 16:00
I have some issue understanding the use of symrdf enable in single session setup. I have one source and target connection to each other with Async mode . What scenario do you think enabling symrdf enable on the Async group will help. I dont see any possibility of a single lun going bad in the Vmax world with thin pool . Can you help me to understand how enabling consistency will benefit
dkakljkml
29 Posts
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June 28th, 2013 16:00
hello Subash,
I have some issue understanding the use of symrdf enable in single session setup. I have one source and target connection to each other with Async mode . What scenario do you think enabling symrdf enable on the Async group will help. I dont see any possibility of a single lun going bad in the Vmax world with thin pool . Can you help me to understand how enabling consistency will benefit
Archuperi721
110 Posts
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June 29th, 2013 22:00
dkakljkml,
How would do you feel that single source and target replication session going to be out of consistent state?
John Toner has given the answer in the third reply...
dkakljkml
29 Posts
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June 30th, 2013 06:00
Hi Archiperi,
As I mentioned earlier, i don't see a scenario where a device will go bad in the RA group . If we where using raid groups , yes in that case there is possibility of a device going bad , but with virtual providing I don't see that case. further I did some testing , I disabled one of the device ( on the source side) in the ra group with asyn mode and consistency enabled on the group, still after doing this it didn't drop the session.
sauravrohilla
859 Posts
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July 1st, 2013 03:00
when you have a single source and single target but spanned across multiple physical ra link..
regards,
Saurabh
dkakljkml
29 Posts
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July 1st, 2013 05:00
Saurabh,
T
Thanks for the reply, I still doubt if one link in a ra port group goes down it will drop the session . Assume we have 4 ports on a ra group, if one port goes bad , I don't think it will the session. I will still continue to replicate through other 3 ports. Correct me if I am wrong
Archuperi721
110 Posts
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July 2nd, 2013 04:00
dkakljkml ,
To my knowledge Raid group / pool device will not have an impact on the replication other than the performance issue on the host.
When you said disabling the RDF1 device that means you have disabled it the host, not on the RDF port?
As long as you have one link out of 4 it won’t drop, other than delayed copy cycle and performance. Link drop will take when you fill up your SRDF DSE pool.
Check the values link limbo and Transmit idle values…
Regards,
Periyakaruppan N (Peri),
SAN specialist
dkakljkml
29 Posts
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July 2nd, 2013 06:00
Hi Archuperi, thank for the response. So from you reply what scenario do you think enable consistency will help with async mode , specially in the case where we have single source single target
Archuperi721
110 Posts
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July 3rd, 2013 22:00
With single source / single target replication I do not see much difference being whether its consistency or not. We can do the MSC cleanup / apply to make clear data copy at DR.
When we are replicating multiple devices from a host / from many device groups then the RDF consistency would give us the result.
e.g., out of 5 devices from a host / device groups, if one device goes not ready on the RDF link then the RDF consistency would do its best part.
Correct me if I am wrong…. Thank you.
Regards,
Periyakaruppan N (Peri),
SAN specialist