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Re: [dm-devel] multibus / failover and EMC CX600

Tore Anderson wrote:
* Hannes Reinecke

That's the dev_loss_tmo setting. Just increase it to something to
your liking.

Oh, sweet.  This knob won't affect how long the layer will hold I/O
before failing it (like lpfc_nodev_tmo), I assume?  (I'm worried about
it taking longer for dm-multipath to detect failed paths).

With newer versions of lpfc you can set /sys/class/fc_rport/rportXYZ/fast_io_fail_tmo to a low value so that IO is failed quickly, and then set the dev_loss_tmo to a high value so the device is not removed quickly.

The only problem may be that there is a race where dm-multpiath could be queueing IO to the scsi layer while the scsi layer is reporting a failure. That IO that was getting queued will then sit in the scsi layer until dev_loss_tmo fires. That is fixed with this patchset
but I never finished testing it out.

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