6.5.1

Table Of Contents
Procedure
1 Browse to the host in the vSphere Web Client navigator.
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.
Identifying Device Connectivity Problems
When your ESXi host experiences a problem while connecting to a storage device, the host treats the
problem as permanent or temporary depending on certain factors.
Storage connectivity problems are caused by a variety of reasons. Although ESXi cannot always
determine the reason for a storage device or its paths being unavailable, the host differentiates between a
permanent device loss (PDL) state of the device and a transient all paths down (APD) state of storage.
Permanent Device Loss
(PDL)
A condition that occurs when a storage device permanently fails or is
administratively removed or excluded. It is not expected to become
available. When the device becomes permanently unavailable, ESXi
receives appropriate sense codes or a login rejection from storage arrays,
and is able to recognize that the device is permanently lost.
All Paths Down (APD) A condition that occurs when a storage device becomes inaccessible to the
host and no paths to the device are available. ESXi treats this as a
transient condition because typically the problems with the device are
temporary and the device is expected to become available again.
Detecting PDL Conditions
A storage device is considered to be in the permanent device loss (PDL) state when it becomes
permanently unavailable to your ESXi host.
Typically, the PDL condition occurs when a device is unintentionally removed, or its unique ID changes, or
when the device experiences an unrecoverable hardware error.
When the storage array determines that the device is permanently unavailable, it sends SCSI sense
codes to the ESXi host. After receiving the sense codes, your host recognizes the device as failed and
registers the state of the device as PDL. For the device to be considered permanently lost, the sense
codes must be received on all its paths.
After registering the PDL state of the device, the host stops attempts to reestablish connectivity or to send
commands to the device.
vSphere Storage
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