Symmetrix RA Groups

start with      `symcfg -sid xxsource list -rdfg all` do the same with remote sid. Also `symcfg -sid xxxx list -ra all -v ` . Both of them will help you to help to ask more questions than you asked already

So basically you have asked all about SRDF basics. I recommend you read SRDF Product Guide for in depth explanations.

Coming back to answer your questions

i)  If i understand correctly, the SRDF devices get replicated using the SRDF directors and the hosts access the SRDF devices using the front end directors. Correct?

YES

ii) What are RA groups?. When i configure new R1 and R2 device pairs , i understand i must add the new devices to the existing/new disk group, do i need to add the new pair to RA groups as well?

RA grp contains replication definitations. Viz Source Symm id,Remote Symm id, Source RDF Director,Remote RDF Director.

The term "adding" devices to RA grp is not very appropiate. It is called "Create". 

iii) If i need to add new R1, R2 pairs to the RA groups as well. Can i add the new pair to any of the existing RA groups?.

Yes you can. Keep in mind that SRDF has different modes viz Sync/Async.Add the devs to the grp which suits your need.

iv) Do all the devices in a device group need to be assigned to the same RA group?. If so, what command will tell which devices currently belong to which RA group?

symrdf -sid xxxx -g testdg query -rdfg 2

testdg contains the Device list you wan't to query.

The role of -rdfg 2 flag is to tell symcli that you want to query the devices in "testdg" and the parameters to fetch the details  are in rdfg 2. As you can see that in this command, there is no mention of the Remote Symmetrix Array. Symcli fetches that info from the RA grp 2.

symdev -sid xxxx show will tell you the RA Grp to which the device belongs to.

You can add devices belonging to different RA grps to a single DG theoritically, but it will serve no purpose.

v)  Is there any pairing between the RA group in Source Symmetrix and RA group in the target Symmetrix?. If there is any pairing, how is the pairing done?

Pairing is b/w devices and not RA grps. The command to create an RA grp by default creates an RA grp on Remote Array too.

vi) If there is any pairing between the RA group in Source Symmetrix and RA group in the target Symmetrix, how is that pairing created?. If i do not put the new devices in the paired RA groups,  will the replication not work? What is the command to check the pairing of RA groups in source and target symmetrix?

symrdf addgrp –label SrdfSync -sid xxx -rdfg 2 -dir 7H -remote_sid yyy -remote_rdfg y -remote_dir 8H

This command creates two RA grps. One on Source Symm and the other on remote symm. The RA grp number is 2.

To get details of existing RA grps, you can run

symcfg -sid xxx list -rdfg all

Remote Replication is a big subject. Although I tried to answer your questions, I would suggest you to go thru SRDF product guide.

Deepak covered a lot for u. One key thing i would mention next is how you create the relation between devices once the RA group in place.

symrdf -sid xxxx createpair -f filename_r1_r2 -est -type rdf1 -rdf_mode=acp_disk -rdfg yy # initial sync is always done w/o using the cache

Super Stuff Deepak

Just to add to it, if you have ASYNC type RA group then you need to put all the devices from that RA group to one DG otherwise you wont be able to manage the devices and you will  get the error.

"All the devices in the SRDF/A session must be managed together when the devices are in async mode"

It only applies to SRDF/A. This does not apply to SRDF /SYNC.

regards,

Saurabh Rohilla

Thank you all for your responses. I really appreciate your help. I will go though the documents suggested and get back to you if i have any doubts.