Can anyone help me understand what constitutes an "initiator" or "target" in the context of single-initiator / single-target SAN fabric zoning methodology?
Is the "initiator" or "target" defined by:
the World Wide Node Name (WWNN)
the World Wide Port Name (WWPN)
the World Wide Name (WWN) a combination of the WWNN and WWPN
If it's the WWNN, that means that a single initiator / target could have multiple WWPNs. E.g. SAN array has a single WWNN with a WWPN per port per controller.
N.B. "initiator" vs "target" doesn't really make any difference, are interchangeable, and is included for context.
I'm not quite sure exactly what you're asking, but, simplistically,
An "initiator" initiates a connection to storage volume
A "target" listens for in-bound connection requests
A WWN uniquely identifies a volume (disk/raid controller/etc) typically fibre channel or iSCSI such that an initiator can identify if it is talking to the same storage via different routes i.e., multi-path.
I'm clear on what the initiator and target do in the communications role.
I'm trying to identify what part of a WWN / WWNN / WWPN / some combination thereof, is used to define an initiator or target.
If an initiator / target is defined as the WWNN, then the initiator / target can have multiple WWPNs associated with it while still being a single initiator / target
If an initiator / target is defined as the WWPN, then the WWNN will have multiple initiators / targets associated with it.
Is the following list two or four initiators / targets?
50:06:01:60:B6:E0:06:34:50:06:01:67:36:38:06:34
50:06:01:60:B6:E0:06:34:50:06:01:68:36:38:06:34
50:06:01:60:88:60:34:71:50:06:01:6A:08:60:34:71
50:06:01:60:88:60:34:71:50:06:01:63:08:60:34:71
There are two WWNNs in the list above:
50:06:01:60:B6:E0:06:34
50:06:01:60:88:60:34:71
There are four WWPNs in the list above:
50:06:01:67:36:38:06:34
50:06:01:68:36:38:06:34
50:06:01:6A:08:60:34:71
50:06:01:63:08:60:34:71
How many initiators / targets are in the list above?
More so why do you say the number that you do?
I can see an argument for two (same as number of WWNNs) and for four (same as number of WWPNs).
What (part of) the four WWNs listed above is an initiator / target?
I question the veracity of that.
The WWN combined with the LUN identifies the volume for a given client. -- However, the same volume very likely can be accessible at other WWN+LUN combinations; e.g. alternate path for the same client, and / or some WWN+LUN for other clients. E.g. ${WWN} and ${LUN} on one client may be one volume while the same ${WWN} and ${LUN} may very well be a different volume on a different client on the same SAN array controller.
Multiple volumes from the same SAN array controller will likely have the same (set of) WWN(s) but with different LUN values.
So the WWN by itself doesn't uniquely identify the volume, not even for the same client.
All the multipathing that I'm used rely on something other than the WWN / WWN,LUN to identify the volume. There is usually a volume ID / serial number / UUID that is used to detect the multiple paths to the same volume and aggregate them into a logical access method.
I found -- what I consider to be -- an authoritative source with a hard answer to my question. I'm sharing in case anyone else ever has a similar question.
The types of zone members used to define a zone may be mixed. For example, a zone defined with the following members: "2,12; 2,14; 10:00:00:60:69:00:00:8a" would contain all the devices connected to switch 2, ports 12 and 14, and the device with the worldwide name "10:00:00:60:69:00:00:8a" (either node name or port name), at the port in the fabric to which it is connected.
So my understanding is that an initiator and target are defined by their 64-bit worldwide name (WWN) and that it's up to the user to determine if they use the WWNN or the WWPN.