Both Fibre Channel and iSCSI use VMFS-formatted block storage as their data structure. Due to the commonalities of both storage transports, a lot of the steps you can take to troubleshoot connectivity and visibility issues overlap and are explained in the following sections.
As we discussed in Chapter 1, Understanding vSphere Storage Concepts and Methodologies, each storage device managed by vSphere is connected by loading a plugin inside the Pluggable Storage Architecture (PSA). The process inside PSA that associates our storage array devices with the proper storage plugins, whether that is the default NMP provided by VMware or a third-party plugin provided by our storage vendor, is called claiming . Claiming is essentially a group of rules called claim rules that contain associations between the storage devices and either the MPP or the NMP.
So why are claim rules important when it comes to troubleshooting...