Noob: Connecting multiple SAN's

[Stevehewitt]

Hi Guys,

New to SAN's so please bare with me whilst I scramble to learn - fraid I'm more of an ethernet man at heart...!

Got two CX300's connected to four server via two Brocade 200E switches in a full mesh redundant fabric. (two paths from each server to either SAN)

We've just purchased two CX4-120, another two Brocade 200E's and four new servers.

I'm planning on setting these up in a similar manner, however once they are all connected is is technically possible for me to connect one of the new switches to one of the old ones?

Or would it be more ideal to simply have a connection from new server to old switch than from new switch to old switch?

I appreciate that it will be faster as each server will have a 2Gbps connection to the old SAN (and 4Gbps to the new one); yet if I use a single connection from old switch to new switch there will only be a single 4Gbps connection contended between all servers - but is it fesiable to do this?

Cheers,




Steve.

"They have the internet on computers now!" - Homer Simpson

 

[baddos]

Do you need to access both SANs from the same hosts?

 

[jjjon]

Steve,

It's certainly feasible to connect up the switches once you have it all set up, but would be a lot cleaner to add the 2 new switches into your existing SAN beforehand, that way you don't need to worry about merging fabrics.
Not sure from above, but if your 2 existing switches are not connected to each other then you can add the new ones to have 2 * 2-switch fabrics - I'd move the storage ports on the 4GB switches and the hosts on the 2GB switches. You'd have to judge how many ISL ports you'd need by the traffic that will be on the switches.

J

 

[SANEngInCO]

Steve,

There are several larger issues here that you will need to deal with. First, the ISL's from switch to switch will take 4 ports away from your hosts and arrays EACH. So if you have 2 ISL's from each switch, you will lose 8 ports from each switch to accommodate them. Second, if you have a host connected to the 2Gbps switch and the storage on a 4Gbps switch and those switches ISL'd together, you will never get above 2Gbps to anything in the environment. Everything is always based on the lowest common denominator and in this case it will be 2Gbps.

I have an environment which contains 8 directors and around 12 non-director SAN switches and we do not have a single ISL in the whole environment. We have divided our environments out by function, string and/or frame that attaches to them. ISL are expensive (licensing), complex to set up and will "cost" at lot of ports on both sides of each connection.

For me, they are not really needed unless you need to transfer data between hosts or arrays such as a DR site, cluster or tiering of data. Without knowing your environment and what exactly you are trying to accomplish, I can't really give you a detailed answer on whether or not connecting the switches via ISL is the "right thing to do." But if you are absolutely dead set on doing it, make sure you have enough ports and that you connect the switches together before adding any hosts, storage or zones. Merging fabrics after the fact is extremely tricky.

Hope this helps you a little.

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