Highlighted
3 Argentum

maximum number RDF devices per RDF group

Jump to solution

I have  vmax250fx running powermax OS, the maximum number of RDF devices is 64k.   I would like to know is there any limit for maximum number of RDF devices can be contained in a RDF group.

Labels (1)
0 Kudos
1 Solution

Accepted Solutions
Highlighted
3 Zinc

Re: maximum number RDF devices per RDF group

Jump to solution

No limit. They can all be in the same RDFG.

View solution in original post

20 Replies
Highlighted
3 Zinc

Re: maximum number RDF devices per RDF group

Jump to solution

No limit. They can all be in the same RDFG.

View solution in original post

Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

Why is there a limit on Dynamic RDF devices at all? And what exactly is an RDF group?

Highlighted
3 Zinc

Re: maximum number RDF devices per RDF group

Jump to solution

Effectively there is not an RDF device limit. If you look at the overall maximum number of devices for the array it it also 64K.

To learn more about RDF groups, check out the "SRDF Groups" section in the SRDF product guide here

Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

Just to be clear, the limit is in fact on all devices in the storage array and not specifically on RDF devices?

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

I've read the SRDF product guide in the section you pointed out, thank you very much for that by the way. What I understood is that there are three RDF groups - RDF1, RDF2 and Dynamic RDF groups, and inside them can be several types of devices such as R1, R11, R21, R2, R22 (support for certain devices is dependant on the enginuity version and on the RDF group). Can you confirm my understanding of the subject?

0 Kudos
Highlighted
3 Zinc

Re: maximum number RDF devices per RDF group

Jump to solution

Correct, all host devices can be RDF.

RDF1 and RDF2 groups are more historic these days. All RDF groups in VMAX and above will be Dynamic.

Just a small correction... there are 3 types of RDF groups (not 3 groups) . There can be many DYNAMIC RDF groups defined in an array.

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

What do you mean by "all host devices can be RDF"?

Why are RDF1 and RDF2 more historic these days?

Could you explain why I would want to create multiple Dynamic RDF groups in an array?

Thankyou so much for the help!

0 Kudos
Highlighted
3 Zinc

Re: maximum number RDF devices per RDF group

Jump to solution

Any symdev than can be presented to a host channel ( FA, iscsi of Ficon port) can be made RDF capable. There are internal only devices in the array so that it what I made the distinction "host devices"

Dynamic RDF groups are user creatable. Prior to Dynamic groups they were considered static and could only be created by EMC.

There are many reasons to have more than one RDF group. SRDF/A and SRDF/S modes cannot both be active on the same RDFG at the same time for example.

I recommend you have a read of the SRDF Product guide and the Solutions Enabler SRDF Family CLI User Guide to understand more about SRDF groups.

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

Got it. In the previous topic, I asked you the same question, didn't pay attention, sorry.

I see why I would want to use several RDF groups when I'm implementing relatively complication solutions such as SRDF/Star, but I really don't see why, for instance,  I would want to create more than one dynamic RDF group per storage array in a SRDF/S solution.

0 Kudos
Highlighted
7 Thorium

Re: maximum number RDF devices per RDF group

Jump to solution

A unique RDF group if you need to replicate between different target arrays, or if you have multiple RDF adapters and you want to have some devices use one set of RDF adapters and another set of devices use another set of RDF adapters.

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

So if I have different arrays then I will use different RDF groups for organization. However, what about just 2 machines (storage arrays) with SRDF/S, why would I create more than one group per array?

What do you mean by RDF adapters? Why wouldn't I just share all the adapters among one group?

0 Kudos
Highlighted
7 Thorium

Re: Re: maximum number RDF devices per RDF group

Jump to solution

LearnEverything wrote:

So if I have different arrays then I will use different RDF groups for organization. However, what about just 2 machines (storage arrays) with SRDF/S, why would I create more than one group per array?

you typically wouldn't for SRDF/S where you can manipulate RDF relationships separately (versus SRDF/A). For example look at the below configuration. I am using 4 RF adapters between array 1234 and 9999, same RA rdfg group 9. We started out with 2 adapters but then upgraded to 4 to give us better write response times on SRDF/S devices.

symcfg -sid 1234 list -ra ALL -switched

Symmetrix ID: 000000001234 (Local)

            S Y M M E T R I X    R D F    D I R E C T O R S

         Local            Group      Link              Remote           

--------------------- -------------- ---- -------------------------------

        Po                                                    Po        

         r                      FLGS FLGS                      r        

Ident    t  RA Grp  T Name       SH   SH  SymmID       Ident   t  RA Grp

------  -- -------- - -------------- ---- ------------ ------ -- --------

RF-1E    4        - -     -      --   --  -            -       -        -

         5        - -     -      --   --  -            -       -        -

         6        - -     -      --   --  -            -       -        -

         7   3 (02) D 1234to5678 ..   X.  000197805678 RF-3E   7   3 (02)

         7  10 (09) D 1234to9999 ..   X.  000196709999 RF-1F   7  10 (09)

RF-2E    4        - -     -      --   --  -            -       -        -

         5        - -     -      --   --  -            -       -        -

         6        - -     -      --   --  -            -       -        -

         7  10 (09) D 1234to9999 ..   X.  000196709999 RF-2F   7  10 (09)

RF-3E    4        - -     -      --   --  -            -       -        -

         5        - -     -      --   --  -            -       -        -

         6        - -     -      --   --  -            -       -        -

         7  10 (09) D 1234to9999 ..   X.  000196709999 RF-3F   7  10 (09)

RF-4E    4        - -     -      --   --  -            -       -        -

         5        - -     -      --   --  -            -       -        -

         6        - -     -      --   --  -            -       -        -

         7   3 (02) D 1234to5678 ..   X.  000197805678 RF-2E   7   3 (02)

         7  10 (09) D 1234to9999 ..   X.  000196709999 RF-4F   7  10 (09)

0 Kudos
Highlighted

Re: Re: maximum number RDF devices per RDF group

Jump to solution

I see, but they are all under the same RDF group (09).

0 Kudos
Highlighted
7 Thorium

Re: Re: maximum number RDF devices per RDF group

Jump to solution

they are in my case but could be in different groups. For example let's say you want to "pin" some devices to use a particular set of RDF adapters because you want to use it for  your ultra response time sensitive devices (Oracle REDO logs for example).  So for those devices you could specify a different group even though it's connecting to the same array.

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

Different RA's have different characteristics? Aren't they all the same adapters connected to the front end of the same type of directors?

How do I assign TDEVs to specific RDF groups?

0 Kudos
Highlighted
7 Thorium

Re: maximum number RDF devices per RDF group

Jump to solution

same characteristics but could have different load based on how many devices are using them. You specify RDF group when you create RDF pair.

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

We use all TDEVs as RDFs as well, but when I provision a LUN I just assign it as Dynamic RDF without other SRDF configurations.

Where in this process do I specify the RDF group?

0 Kudos
Highlighted
7 Thorium

Re: maximum number RDF devices per RDF group

Jump to solution

when you create RDF relationship

symrdf -sid 1234 -f myfilewithsource_target_devices.txt  -type R1 -invalidate R2 -rdfg 11

0 Kudos
Highlighted

Re: maximum number RDF devices per RDF group

Jump to solution

What does the "txt" file consist of as in what format and how does it look like?

0 Kudos
Highlighted
3 Zinc

Re: maximum number RDF devices per RDF group

Jump to solution

Please refer to the Solutions Enabler SRDF CLI Product guide for an explanation on the -f parameter. We are happy to help in the forums but you should really check out the documentation before posing a question here.

0 Kudos