6.0.1

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 grayed out.
The host automatically removes the PDL device and all paths to the device if no open connections to the
device exist, or after the last connection closes. You can disable the automatic removal of paths by seing the
advanced host parameter Disk.AutoremoveOnPDL to 0. See “Set Advanced Host Aributes,” on page 180.
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.
N The host cannot detect PDL conditions and continues to treat the device connectivity problems as
APD when a storage device permanently fails in a way that does not return appropriate SCSI sense codes or
iSCSI login rejection.
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
In the case of iSCSI arrays with a single LUN per target, PDL is detected through iSCSI login failure. An
iSCSI storage array rejects your host's aempts 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 terminates 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,” on page 131.
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 and 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 reconguring your storage devices. When you
perform an orderly removal and reconnection of a storage device, you complete a number of tasks.
1 Migrate virtual machines from the device you plan to detach.
See the vCenter Server and Host Management documentation.
2 Unmount the datastore deployed on the device.
See “Unmount Datastores,” on page 168.
3 Detach the storage device.
See “Detach Storage Devices,” on page 128.
4 For an iSCSI device with a single LUN per target, delete the static target entry from each iSCSI HBA
that has a path to the storage device.
See “Remove Dynamic or Static iSCSI Targets,” on page 98.
Chapter 13 Managing Storage Devices
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