Which of the topology attached in picture is recommended ?
TOPOLOGY A : Catalyst 3750 stack with port-channel to access switch
TOPOLOGY B : Catalyst 3750 without stack ,. ( STP running )
As a general rule I would stack the switches.
Stacking switches gives a couple of advantages such as faster backbone between the switches, redundancy for broken powersupplys, easier management, trunking servers to different hardware and so on.
However that said there is a thing you should ask yourself before stacking.
Stacking binds the two or more switches together as a logical unit.
That means that if you for some reason need to restart the switch it will be offline for more or less 3.5 minutes.
Reasons for restarts includes but are not limited to:
IOS Upgrades (planned)
Software error resulting in a crash
Reloads issued by operator.
Problems affecting the ip stack of the switch stack (wrong ios, configuration errors cpu or memory problems)
Or just the in general, shit happens.
If you can not ever have the switches lost for 3.5 minutes for some reason then maybe a different aproach is advisable.
Fx it might be better to look at a meshed solution (traditional switch design).
But if you have those demands then it might be a better solution to have several stacks with 3750E and a redundant design
Expensive?! Absolutely, but it keeps the network up and about.
HTH and good luck
Whatever floats your boat. If I ever saw two separate switches that has a potential for stacking, I will. I have heard of good arguments as to why these should not be stacked but it all depends entirely upon you.
STP will still be there.
If the switch master in a stack of two (or more, for example) fails, the 2nd one will immediately take-over. The config is shared between all of the stack members anyway.
In my humble opinion, if your stack of 3750 (topology A) is properly cabled up then you can enjoy 32Gb, half-duplex backplane. With Topology B, your main switch only talks in 2 Gb.
I would go for Topology A because this is better suited for a 3750.
Another thing is the configuration. In Topology B, you configure three switches while you only configure two switches with Topology A.