Working with Permanent
Device Loss
In some cases a
permanent device loss (PDL) might occur.
With earlier
releases,
an APD (All Paths Down) event results when the LUN becomes unavailable. The
event is difficult for administrators because they do not have enough
information about the state of the LUN to know which corrective action is
appropriate.
In
5.0, the
host can
determine whether the cause of an APD event is temporary, or whether the cause
is PDL. A PDL status occurs when the storage array returns SCSI sense codes
indicating that the LUN is no longer available or that a severe, unrecoverable
hardware problem exist with it.
has an
improved infrastructure that can speed up operations of upper-layer
applications in a device loss scenario.
Do not
plan for APD or PDL events, for example, when you want to upgrade your
hardware. Instead, perform an orderly removal of LUNs from your
server,
which is described in
Detach a Device and Remove a LUN,
perform the operation, and add the LUN back.