6.5.1

Table Of Contents
4 Select the detached storage device and click the Attach icon.
The device becomes accessible.
Recovering from PDL Conditions
An unplanned permanent device loss (PDL) condition occurs when a storage device becomes
permanently unavailable without being properly detached from the ESXi host.
The following items in the vSphere Web Client indicate that the device is in the PDL state:
n
The datastore deployed on the device is unavailable.
n
Operational state of the device changes to Lost Communication.
n
All paths are shown as Dead.
n
A warning about the device being permanently inaccessible appears in the VMkernel log file.
To recover from the unplanned PDL condition and remove the unavailable device from the host, perform
the following tasks.
Task Description
Power off and unregister all virtual machines that are running on the datastore affected by the PDL
condition.
See vSphere Virtual Machine
Administration.
Unmount the datastore. See Unmount Datastores.
Rescan all ESXi hosts that had access to the device.
Note If the rescan is not successful and the host continues to list the device, some pending I/O or
active references to the device might still exist. Check for any items that might still have an active
reference to the device or datastore. The items include virtual machines, templates, ISO images,
raw device mappings, and so on.
See Perform Storage
Rescan.
Handling Transient APD Conditions
A storage device is considered to be in the all paths down (APD) state when it becomes unavailable to
your ESXi host for an unspecified time period.
The reasons for an APD state can be, for example, a failed switch or a disconnected storage cable.
In contrast with the permanent device loss (PDL) state, the host treats the APD state as transient and
expects the device to be available again.
The host continues to retry issued commands in an attempt to reestablish connectivity with the device. If
the host's commands fail the retries for a prolonged period, the host might be at risk of having
performance problems. Potentially, the host and its virtual machines might become unresponsive.
To avoid these problems, your host uses a default APD handling feature. When a device enters the APD
state, the host turns on a timer. With the timer on, the host continues to retry non-virtual machine
commands for a limited time period only.
vSphere Storage
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