On thing that seems to be a mess with the tmo value that is being inherited from the underlying driver, is that the setting for the scsi layer is significantly different from what multipath calls TMO. In the case I have seen with the lpfc driver this is often set fairly low (HPE's doc references 14 seconds, and this is similar to what my employer is using). parm: lpfc_devloss_tmo:Seconds driver will hold I/O waiting for a device to come back (int) But setting this on the scsi layer causes it to quickly return an error to the multipath layer. It does not mean that the scsi layer removes the device from the system, just that it returns an error so that the layer above it can deal with it. The multipath layer interprets its value of TMO as when to clean up/remove the underlying path that when dev_loss_tmo is hit. TMO is used in both names, but they are not the same usage and meaning and the scsi layer's TMO should not be inherited by the multipath layer, as they don't appear to actually be the same thing. In multipath it should probably be called remove_fault_paths or something similar. This incorrect inheritance has caused issues, as prior to multipath inheriting TMO from the scsi layer, multipath did not remove the paths when IO failed for TMO time. The paths prior to the inheritance stayed around and errored until the underlying issue was fixed, or a reboot happened, or until someone manually removed the failing paths. When I first saw this I had processes to deal with this, and we did noticed when it stated automatically cleaning up paths and it was good since it eliminated manual work, that is until it caused issues during firmware update. HPE's update to infinity will be a response to the inherited TMO change causing issues. On Wed, Dec 12, 2018 at 10:58 AM Xose Vazquez Perez <xose.vazquez@xxxxxxxxx> wrote: > > It's needed by Peer Persistence, documented in SLES and RHEL guides: > https://support.hpe.com/hpsc/doc/public/display?docId=a00053835 > https://support.hpe.com/hpsc/doc/public/display?docId=c04448818 > > Cc: Christophe Varoqui <christophe.varoqui@xxxxxxxxxxx> > Cc: DM-DEVEL ML <dm-devel@xxxxxxxxxx> > Signed-off-by: Xose Vazquez Perez <xose.vazquez@xxxxxxxxx> > --- > libmultipath/hwtable.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/libmultipath/hwtable.c b/libmultipath/hwtable.c > index d3a8d9b..543bacd 100644 > --- a/libmultipath/hwtable.c > +++ b/libmultipath/hwtable.c > @@ -116,6 +116,7 @@ static struct hwentry default_hw[] = { > .prio_name = PRIO_ALUA, > .no_path_retry = 18, > .fast_io_fail = 10, > + /* infinity is needed by Peer Persistence */ > .dev_loss = MAX_DEV_LOSS_TMO, > }, > { > -- > 2.19.2 > > -- > dm-devel mailing list > dm-devel@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/dm-devel -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
