Mesh Vs Core

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Dec 19th, 2008
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Hi all,

We are going to add a new switch (9509) to an existing fabric(with 1 switch 9513).

Here we have two possibilities: Whether to go for core-edge or mesh?

Can someone enlighten me on the pros and cons and suggest me a link which best describes them.


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Overall Rating: 2.8 (4 ratings)
storagemitch Fri, 12/19/2008 - 08:43
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Do you plan to add more switches in the future? I ask because with 2 switches in a fabric, mesh and core will look exactly the same.

IMO core/edge works best for 3+ switches from a scalability, performance and utilization persepctive.

Mesh is good for 3 switches, OK for 4, tricky with 5 and a nightmare beyond that. With a large mesh you end up with so many ISLs that you have to add yet more switches to get some device ports.


red123456 Fri, 12/19/2008 - 10:25
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We probably may go for 2 more switches per fabric in the next 2 years. So need to plan for the future.

Can you suggest me a link which describes the core-edge configuration.


Michael Brown Fri, 12/19/2008 - 10:48
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The MDS 9513 and 9509 are designed for what is known as a 'collapsed core'. You can place the high density port line cards like the 32 and 48 port line cards for server attachment, and also install the line rate line cards like the 12 and 16 port line cards for Storage and Tape system attachment. This way you don't need ports dedicated for ISLs reducing cost since each ISL link is 2 dedicated ports (GBICs) and 1 cable.

There is another concept called locality where you design the SAN such that servers and the storage/tape devices they access are on the same switch. The intent here would be to limit traffic using the ISLs to only what you need to.

I would recommend creating a port channel between the 9509 and 9513, using ports from different line cards if possible on each MDS. This way you are protected against a single line card failing and causing a segmented fabric.

Hope this helps,


inch Fri, 12/19/2008 - 15:17
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I would go for a core/edge design as a mesh can be a pain in the backside to try and trouble shoot.

It will also depend on how many switches you plan to add in the future and the reasons behind adding more switches vs higher density line cards.

What are your reasons for adding another switch?

red123456 Mon, 12/22/2008 - 06:58
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The reasons are to isolate Pros ,Dev and QA.

Finally figured out to go for core-edge.

Thanks all.

inch Mon, 12/22/2008 - 13:32
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VSAN's will let you isolate traffic without the need for new switches (unless you don't want people putting their fat fingers near production cables :)

I hope it all goes well!

OkieNetapp Mon, 12/22/2008 - 17:54
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Mesh - port cost - high - ISL's 2 port per switch. You loose port density at an expensive rate. Especially when you grow.

Mesh - also can be quite combersome to manage and harder to troubleshoot on large scale.

Core / Edge - simple from a 2-tier core edge to 3-tier core edge. It is eaiser to troubleshoot and much easier to maintain.

The place I would possibly setup a mesh is in the core/edge itself on the core switches. This can be done but a very high cost HA solution as well.

Always consider your port cost and future capacity planning as a way to help you determine if your design is feasible or not.

There still not a good SAN modeling tool that engineers could use to base their decisions on that could help ease some of those decisions like yours to make.

You can find several good books on SAN and there are several sites that has help on good SAN design. Only you understand your company needs and requirement today and the future.

You may want to consider how the SAN may look should you use other technologies like FCoE (Fiber Channel over Ethernet).

Also the good key is to reduce cable infrasturcture so you don't crowed your growth of your DC.

I hope this helps a little.


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