topic Re: EVA4400 Cabling in Disk Enclosures

EVA4400 Cabling

dataerror — Fri, 03 Dec 2010 23:19:57 GMT

While reading the SAN design reference guide, it has come to my attention that my EVA4400 may not be cabled correctly.

The current configuration is (cross-cable):

Controller 1
FP1 - Switch 1
FP2 - Switch 2

Controller 2
FP1 - Switch 2
FP2 - Switch 1

The SAN design reference guide indicates that it should be (straight-cable):

Controller 1
FP1 - Switch 1
FP2 - Switch 2

Controller 2
FP1 - Switch 1
FP2 - Switch 2

Everything appears to be working correctly... there are no errors on the EVA or switches, the systems see 4 paths to each LUN and fail-overs work.

Can someone please explain to me what can happen in the current configuration?

Re: EVA4400 Cabling

dataerror — Sat, 04 Dec 2010 00:32:26 GMT

Just thinking about ways to fix this with minimal impact...
Assuming there is little SAN activity, would you recommend that I do the following 'on-the-fly'?

1. Assign all luns owned by controller 2 to controller 1
2. Swap Controller 2 FP's on the switches
3. Correct the zoning on the switches

Would you guys recommend this approach? Do I even need to worry about re-assigning the controller (step 1) since the EVA should technically do this for me.

Re: EVA4400 Cabling

Sivaramakrishna_1 — Sat, 04 Dec 2010 06:59:29 GMT

I didn't found any issues about the kind of configuration you have. But it is generally a good practice of connecting cables as per the design guide.

Make sure that your hosts are installed with Multipathing solution like MPIO for Windows etc. If then you can do it online.

And try to do it in less IO period.

Re: EVA4400 Cabling

Bhavnish Kamboj (BK) — Sat, 04 Dec 2010 08:25:23 GMT

I would suggest keep it as it is until you don't face any bottleneck in your network.

And if you want to change it on the fly then make sure all hosts should have connectivity to all FP ports of both controllers. And as above said do it only in less peak hours only.

BK

Re: EVA4400 Cabling

dataerror — Sat, 04 Dec 2010 17:26:23 GMT

Thanks for the replies.

All my hosts have the EVA FF MPIO drivers installed and although not all are connected to both switches for full redundancy, it shouldn't mater because C1 is on both switches. I'll give it a shot during the next maintenance period.

Does anyone know why some devices are cross-cable and others straight-cable? I'd like to know more about why the SAN guide recommends this cabling practice for the EVA and I can't seem to find further information.

Re: EVA4400 Cabling

Bulent ILIMAN — Sun, 05 Dec 2010 15:42:36 GMT

you should change the cabling,

cross cabling was the old method for Active/Passive controllers of first generation EVA's (EVA3K&5K)

After all EVA's became Act/Act. staignt cabling started to be used. All the odd ports of the controllers to one switch and all the even ones to the other switch.

you dont need to do anything on the host side or the EVA side if you have an empty slot just unplug the port1 of the controller2 and plug it on the switch one. by that way only one port of the controller2 will be unavailable for a short period of time and this is transparent to the hosts.

when ctr2/port1 is up then you can move ctr2/port2 to the second switch.

If you want, you can move ctr2/port1 to the port where ctr2/port2 was plugged before the operation.

that is all, and I myself done this a few times on different EVA's without any issue.