05-03-2017 05:45 AM
We have a 4Gb FC SAN configured from (4) HP branded SilkWorm 5000 switches, (2) in each of our data centers with ISL supported by long-range transceivers to extend an A & B fabric across both sites. We had isolated traffic to the fabrics using hard zoning as was best practice at the time (see example below):
I was asked why we can’t modify the zones as shown below with the thought it’ll provide increased redundancy for multipathing:
My logical answer was that with traffic isolated on two fabrics like we have, you won’t even see some of the target ports from either initiator, but I think they wanted me to see if it was feasible. Is there a way to achieve a zoning configuration that would allow one initiator to access all targets?
I don't think soft zoning would help us achieve what was requested, it seems more likely that I'd have to change the fabric topology. Thank you.
05-04-2017 04:52 AM
I will try and answer given my understanding or your question.
Firstly though, as you probably realise, the 5000 model switches are no longer supported so if redundancy and resiliency are important, I’d discus upgrading to a supported environment with your Equipment provider.
As I understand it, you are currently running a 2 fabric topology – meaning that the 2 fabrics are not connected and are working wholly independently of each other. This is offering you fabric redundancy, so if something goes wrong with the fabric services – then the 2nd fabric provides the continued connectivity.
If this is true, then simply adding the array controller secondary ports to the zones on each fabric will have no effect other than to create stale or non-existent port to the zone and fabric, because these secondary ports do not exist in each respective fabric.
If you are not actually running 2 separate fabrics and all switches are part of the same fabric – then you do not have fabric redundancy, just zone separation. If that is the case, then adding the secondary array ports to the zones would increase the number of possible paths to the array. Though I can not comment on how the array will manage the additional connectivity.
05-04-2017 04:52 AM
If you would like that all the ports of Array Controller A and B see both 2 Hosts HBAs, this means that complete array need to be on a single Fabric where Host HBAs are connect on.
You will be not able to keep 2 Fabrics physically totally independents.
02-28-2018 12:16 PM
I know this one is old but someone I recently spoke with was adamant about the very subject you mentioned so I thought I would reply. We have 2 Brocade fabrics each having 2 connections to each of our SPs for a total of 8 paths--4 paths each fabric.
We used to do the single host initator with single target sp initiator until we migrated to ESXi and decided to try configuring each zone with single host multi-targets.
So we have the ESXi host initator and 4 target initiators per zone--2 SPs from A side and 2 SPs from B side. This configuration allowed us to reduce the number of zones we had to manage. It is not "recommended" but the admin guide mentions both configurations so Brocade doesn't say NEVER DO THIS. They just say depending on the environment, the perferred single/single method avoids RSCN performance concerns when you have mutliple initiators in the same zone.
Again, we've never had problems in a decade but it's definitely "environment specific". The first time we tried it we weren't sure either but that's how we learned it worked for us. Worst case, you have to manage single zones with single initiators assuming your switches support that many and are licensed. We actually got a license limit or technical initiator limite on ours once which was another positive to reducing zoning.
02-28-2018 08:37 PM
We have seen many issues when LUN's are presented via multiple target ports to the initiator. Simply don't do this.
At the end of last year I was involved in a discussion which touches on similar questions. You can look here for more info on that.
Secondly, as you've seen in the previous answers, you won't be ableto do that as your fabrics are physically separated.
Also DO NOT map luns cross-site to a host unless you know exactly what you're doing. Please see here for more info on that.