When you perform storage management tasks or make changes in the SAN configuration, you might need to rescan storage available to your ESXi host.

When you perform VMFS datastore management operations, such as creating a VMFS datastore or RDM, adding an extent, and increasing or deleting a VMFS datastore, your host or the vCenter Server automatically rescans and updates your storage. You can deactivate the automatic rescan feature by turning off the Host Rescan Filter. See Manage Filters for LUNs and vSphere VMFS Datastores.

In certain cases, you need to perform a manual rescan. You can rescan all storage available to your host or to all hosts in a folder, cluster, and data center.

If the changes you make are isolated to storage connected through a specific adapter, perform a rescan for this adapter.

Perform the manual rescan each time you make one of the following changes.

  • Zone a new disk array on a SAN.
  • Create new LUNs on a SAN.
  • Change the path masking on a host.
  • Reconnect a cable.
  • Change CHAP settings (iSCSI only).
  • Add or remove discovery or static addresses (iSCSI only).
  • Add a single host to the vCenter Server after you have edited or removed from the vCenter Server a datastore shared by the vCenter Server hosts and the single host.
Important: If you rescan when a path is unavailable, the host removes the path from the list of paths to the device. The path reappears on the list as soon as it becomes available and starts working again.

Perform Storage Rescan

When you make changes in your SAN configuration, you might need to rescan storage. You can rescan all storage available to your ESXi host, cluster, or data center. If the changes you make are isolated to storage accessed through a specific host, perform the rescan for only this host.

Procedure

  1. In the vSphere Client object navigator, browse to a host, a cluster, a data center, or a folder that contains hosts.
  2. From the right-click menu, select Storage > Rescan Storage.
  3. Specify extent of rescan.
    Option Description
    Scan for New Storage Devices Rescan all adapters to discover new storage devices. If new devices are discovered, they appear in the device list.
    Scan for New VMFS Volumes Rescan all storage devices to discover new datastores that have been added since the last scan. Any new datastores appear in the datastore list.

Perform Adapter Rescan

When you make changes in your SAN configuration and these changes are isolated to storage accessed through a specific adapter on ESXi host, perform rescan for only this adapter.

Procedure

  1. In the vSphere Client, navigate to the ESXi host.
  2. Click the Configure tab.
  3. Under Storage, click Storage Adapters, and select the adapter to rescan from the list.
  4. Click the Rescan Adapter icon.

Change the Number of Scanned Storage Devices

The range of scanned LUN IDs for an ESXi host can be from 0 to 16,383. ESXi ignores LUN IDs greater than 16,383. The configurable Disk.MaxLUN parameter controls the range of scanned LUN ID range. The parameter has a default value of 1024.

The Disk.MaxLUN parameter also determines how many LUNs the SCSI scan code attempts to discover using individual INQUIRY commands if the SCSI target does not support direct discovery using REPORT_LUNS.

You can modify the Disk.MaxLUN parameter depending on your needs. For example, if your environment has a smaller number of storage devices with LUN IDs from 1 through 100, set the value to 101. As a result, you can improve device discovery speed on targets that do not support REPORT_LUNS. Lowering the value can shorten the rescan time and boot time. However, the time to rescan storage devices might also depend on other factors, including the type of the storage system and the load on the storage system.

In other cases, you might need to increase the value if your environment uses LUN IDs that are greater than 1023.

Procedure

  1. In the vSphere Client, navigate to the ESXi host.
  2. Click the Configure tab.
  3. Under System, click Advanced System Settings.
  4. In the Advanced System Settings table, select Disk.MaxLUN and click the Edit icon.
  5. Change the existing value to the value of your choice, and click OK.
    The value you enter specifies the LUN ID that is after the last one you want to discover.
    For example, to discover LUN IDs from 1 through 100, set Disk.MaxLUN to 101.