03-07-2018 01:43 AM
Brocade SANs - a functionality "WWN Based persistent PID". Any personal experience, pls?
We have been asked to switch Fabric to this mode, because of a combination of a new array and legacy hosts. This combination requires SAN in “WWN Based persistent PID” mode. Our Fabric consists from a mix of DCX, B6520 and B5300 switches. From User Guide, it seems to be supported on DCX switches only and it seems to be pretty challenging to turn it ON on large Fabrics.
03-07-2018 08:40 PM
Oef, good luck. You are going down a rabbit hole with this one as it will incur a large administrative task. I can't recall any OS that had these restriction for the last decade. I know HP-UX had some limitations where scsi channels were part of the internal disk address assignment but that is a long time ago.
As for support the feature can be enabled on 7.x and up i think which is supported on all the three platforms you mention.
Again, if I were you I would look for alternatives.
03-13-2018 01:06 PM
Thanks for the advice. Fortunately, we have tested it a little bit and there is at least one pretty serious constrain, so we have no chance to think about it :).
In example, there is a good reason, why the feature is not supported on non-DCX hw: a “wwnAddress” command allow you to add 256 addresses only instead of 4096 records. Pretty limited on switches with many NPIV devices.
By the way, it works even the feature is not activated on all fabrics switches. You are assigned by a pre-defined PID and it is distributed by Name server to other switches.
And the last, but not least, a switch remembers all the changes made in PID persistent mode. Do not think you will disconnect all devices and reboot to get an initial configuration. So think twice during learning curve.
Some devices generate a ‘phantom’ WWN, recorded in a database, unknown to ‘nodefind’ at all.
But it is fair to say that basic features like activating, adding to the db and unbinding WWNs from the db works in the way, someone would expect.
03-13-2018 08:13 PM
It has to do with the 8 bit and 10-bit PID addressing schema. In some large portcount configurations the switch will flip to 10-bit addressing mode which basically means it steals 2 bits from the area id to be included in the PID. This reduces the available area addresses for NPIVdevices from 255 to 64.
03-13-2018 08:14 PM
PS.for other platforms look at the "portaddress" command.