ISL Between Cisco MDS 922i & MDS 9124

emc162504 & emc193070 ( "How to merge two MDS production switches." & "Cisco: How do I create a port channel via cli")

Consider that an ISL port on the 9222i will need you to put the port in a dedicated mode, not shared, so when you create a 4Gb ISL port, out of the available 12Gbps in the 6 port port group you'll end up with 8 Gbps to be shared between the remaining 5 ports.
Port group 1 = ports 1 to 6, port group 2 = ports 7 to 12, port group 3 = ports 13 to 18. Ech group has 12 Gbps and each ISL will take up DEDICATED bandwidth, so you could create 6 ISLs of 2Gbps each (6 x 2 = 12) or 3 ports in 4Gb ISL mode (E or TE mode) which will leave you with nothing for the remaining 3 ports and you'll need to put them out of service.

The first 18 ports on the MDS9222i can be seen as an oversubscribed switch. If you need more dedicated ports, you could place an extra blade in the switch, for example 4 x 10Gb dedicated, 12 x 4Gb dedicated (I think), 24 x 2Gbps dedicated (or take ports out of service on the 24 port blade if you need 4Gb dedicated ports) or 48 ports for dedicated 1Gb each or a mix of 1, 2 and 4 Gb. If you need dedicated bandwidth in 2 or 4 Gb in the 48 port blade, you need to take ports out of service in some port groups.

Thanks RRR ,
We have not configured port groups on the MDS 922i , each port is running independently. We are facing a port crunch on the current switch , so the management has taken the decision to add another switch MDS 9124 and not add another strip of ports because of the cost involved in it . We have decided to merge the 922i and 9124 (16 Port ) via ISL and run the environment with the new ports on MDS 9124 ... How does that sound to you ?

port groups are hardware coded, you cannot rearange them even if you wanted to. Per port group on the 9222i (yes, three 2's) you only have 12Gb of bandwidth to play with.

How many ISL's are there between the 9124 and the 9222i ? Consider the bandwidth you need because the ISL will be a narrow path between the 2 switches. I would use 2 or 3 ISL that make up 1 portchannel. 2 Is probably enough in your case, but it al depends on the load the traffic between the 2 switches.

I have ISLs between my 9222i and 9124 in the lab and haven't had any issues. It's all about deciding on the overall design of the fabric and how much redundancy you want to build in. I recommend that you put one connection to each host on each of the switches for redundancy sake. The other points listed by the other posters are also important to note.

Thank you.

Thanks Guys for all your help

Can anyone guide me to some document which has got some steps which wud help me merge the two switches...