LEARN. PRACTICE. GROW.Concept and mechanism
A SAN lets a host access block storage through a path including interfaces, links, switches, and targets. A LUN presented as a disk does not automatically create an NFS folder or usable filesystem. The project must define who consumes the resource and which layers organize it. Distinguish LUN identity, initiator identity, and target location. In iSCSI, a node name does not imply a fixed IP address. On Linux, a name such as /dev/sdb can change after reboot. Use the WWID and confirmed mapping to relate host and storage before acting on a device.
Guided application
Multipathing aggregates paths to the same device. Four paths to a 500-GiB LUN still represent 500 GiB before overhead, not two thousand. Path count also does not demonstrate four data copies. In a fictional example, production and test LUNs have the same size. Before initializing either, confirm identity, owning application, authorized host, and approved request. No mount does not prove the device is empty: it can contain data or be used directly. An alias copied from another host requires reconciliation because the same friendly name can represent a different LUN. Record these relationships in the operational inventory.
Four paths with the same WWID identify access to the same 500-GiB resource.
Common pitfalls
Paths as copies; sdX as stable identity; size as ownership; LUN as NFS folder.
Related topics: Fibre Channel and LUN access · iSCSI: sessions and security · Multipathing and path states
Confirm identity and consumers before changing the resource.
Reference: RHEL 9 DM Multipath: topology, identity, queue policy, resize and safe removal · DR SAN 2026-09; selected RHEL 9, ONTAP 9 and iSCSI behavior