From mboxrd@z Thu Jan 1 00:00:00 1970 From: shane bradley Subject: multipath.conf and polling_interval option seems misleading Date: Fri, 16 Jan 2009 11:03:04 -0500 Message-ID: <4970AFB8.6090906@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids 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