After reviewing the code and doing some testing I have noticed that
polling_interval did not work as expected.
I had reviewed the description of the option for multipath.conf and it
conflicted with the results that I had got
testing device-mapper-multipath on RHEL4/RHEL5.
$ cat /usr/share/doc/device-mapper-multipath-0.4.7/multipath.conf.annotated
# # name : polling_interval
# # scope : multipathd
# # desc : interval between two path checks in seconds
# # default : 5
# #
# polling_interval 10
---------
The behaviour that I had expected based on the option's description above:
check path 1
wait polling_interval
check path 2
wait polling_interval
check path 1
wait polling_interval
check path 2
wait polling_interval
However after testing the results that I got was(with multipathd -v4):
example:
check path 1
check path 2
wait polling_interval
check path 1
check path 2
wait polling_interval
---------
The behaviour I seen in RHEL4 and RHEL5 was working as design after
reviewing the code and talking to a couple engineers.
The problem it seems is how I was reading the description of the option.
From my results in testing and talking with some engineers the
"polling_interval" option actually means:
"The interval between checking all possible paths for all multipath paths"
----------
1) Is my assumption correct that "polling_interval" actually means:
"The interval between checking all possible paths for all multipath paths"
2) What is a better way to describe the "polling_interval" option?
3) Shouldn't we make it clearer for people who don't that that much
experience with multipathing?
--sbradley
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