6.5.1

Table Of Contents
The vSphere Web Client displays the following information for the device:
n
The operational state of the device changes to Lost Communication.
n
All paths are shown as Dead.
n
Datastores on the device are not available.
If no open connections to the device exist, or after the last connection closes, the host removes the PDL
device and all paths to the device. You can disable the automatic removal of paths by setting the
advanced host parameter Disk.AutoremoveOnPDL to 0. See Set Advanced Host Attributes.
If the device returns from the PDL condition, the host can discover it, but treats it as a new device. Data
consistency for virtual machines on the recovered device is not guaranteed.
Note When a device fails without sending appropriate SCSI sense codes or an iSCSI login rejection, the
host cannot detect PDL conditions. In this case, the host continues to treat the device connectivity
problems as APD even when the device fails permanently.
Permanent Device Loss and SCSI Sense Codes
The following VMkernel log example of a SCSI sense code indicates that the device is in the PDL state.
H:0x0 D:0x2 P:0x0 Valid sense data: 0x5 0x25 0x0 or Logical Unit Not Supported
For information about SCSI sense codes, see Troubleshooting Storage in vSphere Troubleshooting.
Permanent Device Loss and iSCSI
On iSCSI arrays with a single LUN per target, PDL is detected through iSCSI login failure. An iSCSI
storage array rejects your host's attempts to start an iSCSI session with a reason Target Unavailable.
As with the sense codes, this response must be received on all paths for the device to be considered
permanently lost.
Permanent Device Loss and Virtual Machines
After registering the PDL state of the device, the host closes all I/O from virtual machines. vSphere HA
can detect PDL and restart failed virtual machines. For more information, see Device Connectivity
Problems and High Availability.
Performing Planned Storage Device Removal
When a storage device is malfunctioning, you can avoid permanent device loss (PDL) conditions or all
paths down (APD) conditions. Perform a planned removal and reconnection of a storage device.
Planned device removal is an intentional disconnection of a storage device. You might also plan to
remove a device for such reasons as upgrading your hardware or reconfiguring your storage devices.
When you perform an orderly removal and reconnection of a storage device, you complete a number of
tasks.
vSphere Storage
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