LEARN. PRACTICE. GROW.Concept and mechanism
Growing a LUN crosses several layers. After increasing the array resource, host paths need to recognize the new size; the multipath map and upper layers also require appropriate treatment. The RHEL example includes rescanning every SCSI path and resizing the map, but the filesystem step depends on its type and whether partitions or LVM exist. Do not copy a command from a simple example into every configuration. Confirm application-usable capacity. For firmware changes, consider the supported combination of host, driver, HBA, fabric, and array, including recovery, instead of approving solely because a version is recent.
Guided application
Removal follows the stack from top to bottom: consumers released, pending I/O completed, and references removed before withdrawing resource access. An absent mount does not cover logical volumes, raw access, or other hosts. In a fictional decommission, the new LUN works but references to the old one remain; deletion must wait for evidence of release and applicable retention. After maintenance, confirm expected paths and resilience, not just one read through the surviving path. Give RUN a host-LUN-WWID-path map, alerts, expected states, owners, and validated procedures. Course scenarios are illustrative; no SAN connections, zoning changes, or failures on real equipment were executed.
The new destination being available does not prove consumers released the old one.
Common pitfalls
One rescan as complete growth; recent version as compatibility; unmounted source as released source; closed window as restored resilience.
Related topics: Topology and identity · Fibre Channel and LUN access · iSCSI: sessions and security
Close the change with evidence of access, redundancy, recovery, and operational autonomy.
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