topic Re: Changing LUN IDs in ONTAP Discussions

Changing LUN IDs

TMADOCTHOMAS — Wed, 04 Jun 2025 23:13:38 GMT

I have completed several LUN transitions from 7 Mode to Cluster Mode using the 7 Mode Transition Tool successfully, but this past weekend we had a failure. The Windows cluster hosting the LUNs that I was trying to migrate is the only one that already has a few LUNs on cdot, as well as 7-mode LUNs I'm trying to transition. The 7MTT choked when it saw that the IQN already existed, so it didn't map the 7-mode LUNs. I mapped them manually before restarting the Windows hosts, but then we had LUN ID conflicts between the 7-mode and cdot LUNs. I had to rollback to transition.

I believe I have a resolution to this problem, but would love to get feedback from any of you that might have a comment. Here's what I'm planning to do:

Have the DBA’s turn off and disable SQL services for the instance hosted on cdot LUNs.
Use SnapDrive to disconnect the cdot LUNs.
Unmap the cdot LUNs and remove the cdot initiator groups, which of course removes the LUN IDs.
Have the Server Engineering team shut down all nodes of the Windows cluster.
Allow the 7-Mode Transition tool to transition the 7-Mode LUNs as it normally does, including LUN mappings (as a backup, I would have commands ready to manually do this if necessary, but this time with the LUN IDs added to the commands).
Reboot the cluster nodes and verify that the 7-Mode LUNs transitioned successfully and are functioning.
Reconnect the LUNs that had already been on cdot via SnapDrive, which should assign them new non-conflicting LUN IDs.

Anyone see a gap or flaw in this plan? Any recommendations?

Re: Changing LUN IDs

marcusgross — Tue, 29 Sep 2015 09:26:35 GMT

Hi,

Windows is identifying the disks using the signature on the disk. It doesn't matter what LUN mapping ID it have.

You have to make sure that's unique.

Marcus

Re: Changing LUN IDs

TMADOCTHOMAS — Tue, 29 Sep 2015 19:58:13 GMT

Thanks. So if I remove the cdot LUNs and the initiator groups and then remap them after the other LUNs transition, are you indicating that won't resolve my issue? We'll still potentially have a conflict due to the signature? If so, how can I strip the existing signature off of the cdot LUNs?

Re: Changing LUN IDs

TMADOCTHOMAS — Wed, 30 Sep 2015 15:08:35 GMT

So I reviewed the LUNs and they each have unique serial numbers. As long as that is the case, from what I've read, the signatures won't change. Any thoughts?

Re: Changing LUN IDs

marcusgross — Thu, 01 Oct 2015 10:42:06 GMT

Hi,

Windows is writing a serial to the LUNs, it's not the Netapp LUN serial.

1) create the snapmirror, let it be in sync

1a) stop the Windows cluster and make sure that's not starting if server is rebooted

2) shutdown the server

3) unmap the LUNs

4) update, quiesce and break the snapmirror

5) map the LUNs on the destination filer

6) start the server

7) rediscover the disk in windows

You don't need 7MTT or SnapDrive for this.

Just pure comandline 🙂

Re: Changing LUN IDs

TMADOCTHOMAS — Thu, 01 Oct 2015 17:10:55 GMT

Thanks Marcus. Are you recommending unmapping and remapping ALL of the LUNs, or just the ones I'm planning to unmap/remap? If so, what is the purpose?