LUN ID

[saranraj456]

Hi All,

Does LUN id in netapp filer is used for any reference purpose ?.if so,how it would refer.

Is it been going to have any influence on host end?

Cheers,

Saran

[jacint]

Hi,

the host identifies the LUN by the LUN ID:

"A LUN must have a unique identification number (ID) so that the host can identify and access the

LUN."

cheers,

Jacint

[arunchak]

Yea, Lun id is always used to differentiate the LUNs uniquely.

Hey we can also use the info in this file "/proc/scsi/scsi" to find whether the LUN is from NetApp or whether it is from other vendors with their specific LUN id's (as we were discussing in the post http://communities.netapp.com/message/61532#61532):

[root@warspite ~]# cat /proc/scsi/scsi

Attached devices:

Host: scsi0 Channel: 00 Id: 00 Lun: 00

  Vendor: IBM-ESXS Model: CBR036C31210ESFN Rev: DFQG

  Type:   Direct-Access                    ANSI SCSI revision: 04

Host: scsi0 Channel: 00 Id: 01 Lun: 00

  Vendor: IBM-ESXS Model: ST336607LC    FN Rev: B25H

  Type:   Direct-Access                    ANSI SCSI revision: 03

Host: scsi0 Channel: 00 Id: 08 Lun: 00

  Vendor: IBM      Model: 25P3495a S320  1 Rev: 1

  Type:   Processor                        ANSI SCSI revision: 02

Host: scsi3 Channel: 00 Id: 00 Lun: 00

  Vendor: NETAPP   Model: LUN              Rev: 7330

  Type:   Direct-Access                    ANSI SCSI revision: 04

Host: scsi3 Channel: 00 Id: 00 Lun: 01

  Vendor: NETAPP   Model: LUN              Rev: 7330

  Type:   Direct-Access                    ANSI SCSI revision: 04

Host: scsi3 Channel: 00 Id: 00 Lun: 03

  Vendor: NETAPP   Model: LUN              Rev: 7330

  Type:   Direct-Access                    ANSI SCSI revision: 04

Thanks,

  Arun

[saranraj456]

Do we need to have the same LUN ID across ,when we are using LUNs to cluster servers?

[jacint]

hi,

when you provision a LUN for a Cluster, usually you create an igroup which contains the FC or iSCSI address of the HBAs from all the Cluster nodes. When you provision the LUN and select the appropriate igroup, you'll select the LUN ID, which will be the same for all cluster nodes in this way.

[saranraj456]

here i had a seperate igroup for each node in cluster

[jacint]

I'd recommend to use a single igroup. Here's what SAN Administration Guide says:

"Typically, you want all of the host’s HBAs or software initiators to have access to a LUN. If you are using multipathing software or have clustered hosts,

each HBA or software initiator of each clustered host needs redundant paths to the same LUN. "

[saranraj456]

the recommendations are, invidual igroup in my case to map a new LUN should i have to maintain same LUN ID ?

[arunchak]

Hi,

LUN id is used to identify the LUN uniquely in the mapped Host. What exactly are you trying to achieve here? If you are mapping two LUNs to the same host then do not have same LUN id.

[saranraj456]

Arun,

We have a 2 node cluster (active /passive) server with two igroups separately ,in regards to LUN id do we need to do have the same  ID for both igroups.If it is not be the same what would be  impact.

Saran

[arunchak]

Hi,

Are you trying to map single LUN to 2 igroups. AFAIK you can have different LUN id there should not be any impact. LUN id is to identify the LUN from host side.

Thanks

  Arun

[johannbell]

saranraj456, I recommend using the same LUN ID for the same LUN to all hosts in the cluster.

This will prevent confusion and mistakes later. Use the LUN ID as a unique identifier for those hosts to that storage system.

If you end up with the same LUN having multiple IDs across different hosts in the same cluster, you could cause future administrators some major headaches, particularly during DR or failover situations.

[saranraj456]

other than administrative problem , does it have any other implications on the host end.

Saran