HI Michael, > AFIK As long as the paths are available irrespective of the path is > moved to marginal path group or not multipathd will keep sending the > send path tester IO (TUR) to check the health status. > >You can change the multipathd code. You mean to say don't send the TUR commands for the devices under marginal path groups ? At present the multipathd checks the device state. If the device state is "running" then the check_path Will issue a TUR commands at regular intervals to check the path health status. Regards, Muneendra. > -----Original Message----- > From: Mike Christie [mailto:michael.christie@xxxxxxxxxx] > Sent: Tuesday, October 20, 2020 12:15 AM > To: Muneendra Kumar M <muneendra.kumar@xxxxxxxxxxxx>; Hannes Reinecke > <hare@xxxxxxx> > Cc: linux-scsi@xxxxxxxxxxxxxxx; jsmart2021@xxxxxxxxx; > emilne@xxxxxxxxxx; mkumar@xxxxxxxxxx > Subject: Re: [PATCH v3 05/17] scsi_transport_fc: Added a new rport > state FC_PORTSTATE_MARGINAL > > On 10/19/20 1:03 PM, Muneendra Kumar M wrote: >> Hi Michael, >> Regarding the TUR (Test Unit Ready)command which I was mentioning . >> Multipath daemon issues TUR commands on a regular intervals to check >> the path status. >> When a port_state is set to marginal we are not suppose to end up >> failing the cmd with DID_TRANSPORT_MARGINAL with out proceeding it. >> This may leads to give wrong health status. > > > If your daemon works such that you only move paths from marginal to > active if you get an ELS indicating the path is ok or you get a link > up, then why have multipathd send path tester IO to the paths in the > marginal path group? > They do not do anything do they? > > > >> Hannes/James Correct me if this is wrong. >> >> Regards, >> Muneendra. >> >> -----Original Message----- >> From: Muneendra Kumar M [mailto:muneendra.kumar@xxxxxxxxxxxx] >> Sent: Monday, October 19, 2020 11:01 PM >> To: 'Hannes Reinecke' <hare@xxxxxxx>; 'Michael Christie' >> <michael.christie@xxxxxxxxxx> >> Cc: 'linux-scsi@xxxxxxxxxxxxxxx' <linux-scsi@xxxxxxxxxxxxxxx>; >> 'jsmart2021@xxxxxxxxx' <jsmart2021@xxxxxxxxx>; 'emilne@xxxxxxxxxx' >> <emilne@xxxxxxxxxx>; 'mkumar@xxxxxxxxxx' <mkumar@xxxxxxxxxx> >> Subject: RE: [PATCH v3 05/17] scsi_transport_fc: Added a new rport >> state FC_PORTSTATE_MARGINAL >> >> Hi Michael, >> >> >>> >>> >>> Oh yeah, to be clear I meant why try to send it on the marginal path >>> when you are setting up the path groups so they are not used and >>> only the optimal paths are used. >>> When the driver/scsi layer fails the IO then the multipath layer >>> will make sure it goes on a optimal path right so you do not have to >>> worry about hitting a cmd timeout and firing off the scsi eh. >>> >>> However, one other question I had though, is are you setting up >>> multipathd so the marginal paths are used if the optimal ones were >>> to fail (like the optimal paths hit a link down, dev_loss_tmo or >>> fast_io_fail fires, etc) or will they be treated like failed paths? >>> >>> So could you end up with 3 groups: >>> >>> 1. Active optimal paths >>> 2. Marginal >>> 3. failed >>> >>> If the paths in 1 move to 3, then does multipathd handle it like a >>> all paths down or does multipathd switch to #2? >>> >>> Actually, marginal path work similar to the ALUA non-optimized state. >>> Yes, the system can sent I/O to it, but it'd be preferable for the >>> I/O to be moved somewhere else. >>> If there is no other path (or no better path), yeah, tough. >> >>> Hence the answer would be 2) >> >> >> [Muneendra]As Hannes mentioned if there are no active paths, the >> marginal paths will be moved to normal and the system will send the io. >> >> Regards, >> Muneendra. >>
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