What does no_path_retry=NULL mean?

["Ty! Boyack" <ty@nrel.colostate.edu>]

I've been trying to understand what the default behavior should be if
no_path_retry is not set in the multipath.conf file.  The annotated
version describes (somewhat) what happens with values of queue, fail, or
n>0, but says the default is NULL, and does not say what behavior NULL
produces.

The reason for the question is a situation where a highly-available
iscsi target undergoes failover from one node to another, and the iscsi
initiators see all their multiple paths fail during that transition
time, which takes 5-120 seconds.  I had set no_path_retry to queue,
thinking it would queue until the paths come back, but it seems to stop
checking the path status and queue forever.  Is that expected?  Or 
should no_path_retry=queue stop queuing (but continue checking the 
paths) and send both queued and new requests when the paths are 
available again?  With it set to queue it hangs all I/O requests until I 
restart multipathd, at which point I expect that all queued data is 
lost.  It will stay in the queued state for hours/days even though the 
paths are back if no action is taken.

This is on fedora 9, the default device-mapper-multipath rpm, version
0.4.7, release 16.fc9.  path_checker=readsector0, and poling_interval=10.

Thanks for helping me understand what is happening here.

-Ty!



-- 
-===========================-
  Ty! Boyack
  NREL Unix Network Manager
  ty@nrel.colostate.edu
  (970) 491-1186
-===========================-