Interconnect of switches for two locations

[vlho]

Hi advisors,

I have two HP P4300 boxes and it will be installed in two locations/buildings (same IP segment).

Because I requires full redundancy I need to use four switches (HP 2910al).

I remark that I will have two or three servers on every location.

But I'm not sure how to interconnect it.

　

I think that three variants of intecconnects are possible:

A/ "cross" interconnect

see attachment A

Note: ports 21 and 22 are in Trunk

This variant is in my opinion less suitable because spanning tree will block 3 ports (for example sw3 p24, sw4 p23, sw4 p24) and therefor connection between both locations will be 1Gbps only.

　

B/ "direct" (square) interconnect

see attachment B

Notes:

- ports 21 and 22 are in Trunk

and in difference of variant A

- ports 23 and 24 are in Trunk too

In this case spanning tree will block ports p23 and p24 on switch sw3 for example and therefor connection between both locations will be 2x 1Gbps.

C/ cross interconnect (same as in variant A) but without "red" connections

What variant is right or the best from point of view on redundancy and performance and why?

Or do you recommend another interconnect solution?

Thanks.

[oikjn]

I"m not familiar with the 2910, can you not trunk the fiber ports?  If you COULD, I would consider using the two ports connected to the same switches by fiber, if you CAN'T, I would cross the cables for redundancy.  Give you are connect to both switches at the VSA, if you trunk your fiber, you can get two GB bandwidth across the sites, but you risk loss of connection IF you lose the wrong two switches at both sites, if you connect all four to all four, then you can lose either of the two sitches on both sites at the same time and not have a data availabity problem....  for our comapny, I would probably go w/ the trunked fiber, but if you don't want to risk the dual switch failure problem then I would avoid that trunk.  I'm also not sure how long the typical uptime is for a 2910, but any time you reboot a switch, the "sister" switch at the other site will lose its direct link to the remote site which might cause some MPIO excitement, but should be managable (I suggest you test before going into production).