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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