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New Member

Fake Storage wwpn

Hi,

Is there a way to fake the WWPN of the Storage for the host?

the situation is as follows: I have migrated a LUN from an old Storage to a new SAN Storage.

Zones and LUN masking are correct and the Host is able to reach the new LUNs.

I am receiving  an error from the application that the disk cannot be found (the application have a hard coded path of the disk)

is there any configuration on the N5K to fake the WWPN for the host? so that migration will be transparent to the application?

Hope I was clear

thanks in advance

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Fake Storage wwpn

Shadow,

The old FCID is embedded in the attribute information of the hdisk# itself. Which you can see using the aix command, lsattr -El hdisk#.  Look for the field called "scsi_id"  It will have a corresponding value displayed in hex like 0xa90000.

In the FCID of the hdisk, the bolded part above "a9", is the domainID. 

As far as deleting the old mapping, I didn't know you moved to a new switch.  So probably what you have on your system is twice as many hdisks as you had before.  You've got the old ones in probably the defined state, and new ones that you could potentially access.  There's two options as this point:

  1. Reconfigure Oracle to use the new hdisks, then rmdev the old/defined ones. This requires no changes to the switch (but you should enable both Persistent FCID and Static Domains for the VSAN the array is in).
  2. Reconfigure the VSAN that the storage is in to have the correct domainID and the correct FCID.  This process will most likely be disruptive to the devices on this particular switch in VSAN you are reconfiguring.  Mainly because there's a pretty good chance that the running domainID in the VSAN is not the same as the one that you need it to be (as found in the lsattr command).

This is not an overly complex or unique problem, I see this come up all the time in AIX environments, especially when replacing old FC switches with new ones.   As you're looking to make a specific wwpn have a specific FCID.  Working with Persistent FCIDs and Static Domain IDs is documented in the Configuration Guides (look for the section on configuring domains) and in the Cisco Storage Networking Cookbook.

Since it can be disruptive to other devices on the switch, if you're unfamiliar with it, I would seek direct help from your next level of support as this forum isn't exactly the best medium for this specific procedure.

-Seth

5 REPLIES
New Member

Fake Storage wwpn

Shadow,

Is your server running AIX/HPUX?  As these often have the FCID (not the WWPN) embedded into the device-path.  If this is the case you don't need to change the wwpn of the array, but you can use persistent FCID configuration within the VSAN to assign the old FCID to the new storage arrays wwpn.  You may need to delete the old mapping as wwpn:FCID is a 1:1 mapping.

The n5k doesn't have the ability to alter wwpns, but since it assigns FCIDs, it does have the ability to assign ones that you specify.

Let me know if you need more information,

-Seth

New Member

Fake Storage wwpn

Hi Seth,

Thanks for the reply, the server is an AIX server with Oracle Database that is mapped to several RAW LUNs.

Can you please clarify? How can I know the old FCID? (I have also migrated from IBM SAN Switch to N5K, so which command should I run on the OS to get the Old FCID?

What do you mean by "You may need to delete the old mapping as wwpn:FCID is a 1:1 mapping" ?

Can you provide me with a configuration template.

I appreciate your help

New Member

Fake Storage wwpn

Shadow,

The old FCID is embedded in the attribute information of the hdisk# itself. Which you can see using the aix command, lsattr -El hdisk#.  Look for the field called "scsi_id"  It will have a corresponding value displayed in hex like 0xa90000.

In the FCID of the hdisk, the bolded part above "a9", is the domainID. 

As far as deleting the old mapping, I didn't know you moved to a new switch.  So probably what you have on your system is twice as many hdisks as you had before.  You've got the old ones in probably the defined state, and new ones that you could potentially access.  There's two options as this point:

  1. Reconfigure Oracle to use the new hdisks, then rmdev the old/defined ones. This requires no changes to the switch (but you should enable both Persistent FCID and Static Domains for the VSAN the array is in).
  2. Reconfigure the VSAN that the storage is in to have the correct domainID and the correct FCID.  This process will most likely be disruptive to the devices on this particular switch in VSAN you are reconfiguring.  Mainly because there's a pretty good chance that the running domainID in the VSAN is not the same as the one that you need it to be (as found in the lsattr command).

This is not an overly complex or unique problem, I see this come up all the time in AIX environments, especially when replacing old FC switches with new ones.   As you're looking to make a specific wwpn have a specific FCID.  Working with Persistent FCIDs and Static Domain IDs is documented in the Configuration Guides (look for the section on configuring domains) and in the Cisco Storage Networking Cookbook.

Since it can be disruptive to other devices on the switch, if you're unfamiliar with it, I would seek direct help from your next level of support as this forum isn't exactly the best medium for this specific procedure.

-Seth

New Member

Fake Storage wwpn

A couple of Questions:

1. Are you using some kind of multipathing software?

2. Is it actually the APP that has the path/FCID hard coded or is it the OS

Pre-empting the answers being yes and the OS (all bets are off if not), then you shold be able to delete the paths for one fabric and re-learn them and then the same for the second fabric.  All online with no ill effects.  I know this process works as I've done it MANY times.

Steven

New Member

Fake Storage wwpn

I am rechecking the Situation.

One additional think can i set a static fc domain for vsan to 5

And add a static fcid that does not start with 5 ?

Thanks

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