On 11/09/2016 07:49 AM, Hannes Reinecke wrote: > On 11/08/2016 07:52 PM, Xose Vazquez Perez wrote: >> On 07/15/2016 08:48 AM, Hannes Reinecke wrote: >> >>> Recent kernels have an 'access_state' attribute which allows >>> us to read the asymmetric access state directly from sysfs. >> >> Hi Hannes, >> >> with this patch it's impossible to select/autodetect ALUA. >> sysfs always takes precedence over alua. >> >> "detect_prio no" was added to overrides section, to make >> it work again. >> >> SLES 12-SP2 >> >> Thank you. >> > But this was precisely the idea. > (After all, it says 'auto-detect', right?) > > For ALUA-capable arrays we have a reliable priority detection with the ALUA device-handler. > So it's far preferable to use the sysfs-provided information (as they are populated by the ALUA device-handler); the ALUA prioritizer in multipath-tools will be used as a fallback in case the device > handler isn't loaded or the sysfs files are not present. > Using the sysfs handler has the neat side effect that you don't need to do I/O for detecting the priority, thereby eliminating one possible cause for multipath being stuck during failover. Thanks for the explanation. As collateral effect, because the sysfs-handler output is too brief, the asymmetric access state(aas) was lost: Dec 07 19:26:51 | sda: prio = sysfs (detected setting) Dec 07 19:26:51 | sda: sysfs prio = 50 ---- Dec 07 19:26:29 | sdc: prio = alua (detected setting) Dec 07 19:26:29 | reported target port group is 1 <----- lost Dec 07 19:26:29 | aas = 80 [active/optimized] [preferred] <----- lost Dec 07 19:26:29 | sdc: alua prio = 50 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
