Use vSphere path properties to prevent drastic errors with storage resources

Managing storage in vSphere is a critical practice and can have drastic consequences if you make an error. Rick Vanover shows how to ensure which LUN is which for iSCSI targets.

I hate having discussions with team members about which storage resources are which. You know that you have to be positive when a LUN is to be expanded, deleted, reformatted, or otherwise interacted with on the storage controller, or there could be very serious consequences.

The good news here is that the vSphere Client lets us very easily see which LUN is which when we reconcile with the storage controller. While unintuitive, the magic is to use the Path Policy property to concretely identify the VMFS datastore to the LUN. This becomes especially useful if you “do everything right” in storage practices, such as making every LUN the same size. I’ve seen some vSphere environments where this problem is avoided by using multiple sizes for LUNs such as 1100 GB, 1104 GB and 1108 GB just so they can easily tell which LUN corresponds to which datastore.

In my home lab, I have three iSCSI LUNs provided by a Drobo storage unit. From there, Figure A shows the information in the storage area of the configuration tab of one of the hosts:

Figure A

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We can easily connect the datastore to the LUN on the storage processor (in this case a Drobo) by clicking on the properties of the datastore (highlighted above in green). From the properties of the datastore, we can also view properties of the multipathing for the volume. This is where the actual LUN number is located, which the storage processor uses to refer to the path to the iSCSI target. This is shown in Figure B below:

Figure B

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I can then correlate the LUN ID that I get from the multipathing to the data that is reported from the storage system. Each storage system will display this information differently, but in the case of iSCSI storage networking, the iSCSI target is identified in the path on the ESXi host in the vSphere Client. The other end of this configuration is shown in the Drobo Dashboard (Storage management tool) for this same LUN in Figure C:

Figure C

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There are a number of ways to manage storage, and every storage system may show up differently and have different management techniques. The multipathing policy properties are probably the most consistent way to connect this data in the vSphere Client (command line options exist also). What tricks do you use to determine which LUN is which? Share your comments below.