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method of mapping LUNs

Created: 06 Jun 2013 • Updated: 07 Jun 2013 | 7 comments
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How to identify LUNs presented from storage devices (SAN or iSCSI)?
Let say I am building 2 nodes VCS cluster with fencing and several volumes. I use HA Storage Foundation suite.
I create necessary LUNs on storage servers and present them to both nodes.
Then I go to each node and see how those LUNs look like. Well, they all locally mapped as sdb, sdc, etc.
Only size of these LUNs roughly allows to tell which LUN is which and which storage server it came from.
In case of several differently sized LUNs it is probably easy, but what if I have many, many LUNs with identical sizes.
It can very much be possible that sdb on node 1 is not sdb on node 2.
So far, when I create LUNs myself I try to create them with slightly different sizes, so that only one device from one storage server available to pair it with identical in size device from another server.
Is there a methodology to identify each device surely?
Leonid

Operating Systems:

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mikebounds's picture

When a LUN is created on the san it is given a target number and this number appears after the "d" in the device name - so for instance c1t1d4 has a target number of 4.

Mike

UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows

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rsharma1's picture

Setting enclosure based naming scheme singnificantly helps you identify luns between your backend storage array and VxVM. The last part of ebn is the array volume ID (AVID) which will be same as what your storage array UI would display. An example of EBN lun is: hitachi_usp-vm0_075b - so you'd instantly know this lun comes from which array and this corrorponds to the 07:5b array volume ID on this array.

To set enclosure based naming use: vxddladm set namingscheme=ebn
You can use 'vxdisk -e list' to view corrosponding mapping of the enclosure based names and the native OS devices.

Additionally if you have VOM (or the VRTSsfmh package installed) the wrapper command 'vxlist disk' may be used. For example:

/opt/VRTSsfmh/bin/vxlist -l disk storwizev70002_0011c0

 

vostrushka's picture

To mikebounds:

That is correct, but it does not mean that mapping on the cluster node will be the same. The clister node can map it differenly even after reboot. The iSCSI even worse in this respect.

Actually, the naming on the storage site its very much depend on storage vendor taste. EMC Clarion we have do not do that, at least I have not seen this common format you've mentioned.

What I am after is the methodology that can be applied disregards of storage vendor specifics.

I think that information from storage server about particular LUN (SAN or iSCSI) get passed to the client, but I do know where to look this kind of details and see that one-to-one relation from mapped sd{ID} on the cluster node, LUN ID passed to the cluster node and the same LUN ID on storage device.

Leonid

vostrushka's picture

To rsharma1:

This is interesting. Did you try this with iSCSI LUNs.

The only thing I suspect that this solution can be vendor specific. Will it work with EMC provided disks or iSCSI disks?

I'll try this on my test setup.

Leonid

rsharma1's picture

Enclosure based naming will work for mostly all arrays -including EMC [all those mentioned in the hardware compatibility list (HCL)]. Please check the HCL for the specific SF release you're using. This works for iscsi luns as well -but better doublecheck the specific SF release HCL for the exceptions.

 

SOLUTION
vostrushka's picture

Thank you all. All suggestions were usefull.

I'll try these things now.

Leonid

mikebounds's picture

By the way, if you also need mapping from sd{ID} to Veritas disk on Solaris then see https://www-secure.symantec.com/connect/downloads/relating-devices-reported-solaris-sar-utility-vxvm-disks

Mike

UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows

If this post has answered your question then please click on "Mark as solution" link below