Hi, the path_grouping_policy is only responsible for the path grouping. The "emc" prioritizer here, attributes a prio to each path. Priorities of paths in the same group are aggregated into a pathgroup priority. The pathgroup with the highest priority is activated.
Best regards, Christophe Varoqui www.opensvc.com On Tue, Mar 8, 2016 at 1:03 PM, Bernd Broermann <[email protected]> wrote: > Hello, > > > Does "group_by_serial" activate the "low latency" path ? > > There are two servers which have a separate path to a EMC VPLEX box in > different Data centers ( DC1 , DC2 ) . > > Because of latency the paths are grouped by the serial number of the VPLEX > box. > > > > > DC1 DC2 > > +------------+ +------------+ > | Server 1 | | Server 2 | > +------------+ +------------+ > | \ / | > | \ / | > | \ / | > | \ / | > | X | > | / \ | > | / \ | > | / \ | > | / \ | > +------------+ +------------+ > |disk VPLEX A| |disk VPLEX B| > +------------+ +------------+ > > > As I expected the paths are grouped and the path to the "nearest" disk( > VPLEX) is active. > > Is this an coincidence or does it work as designed ? > > I didn't find something enlightening in the dm documentation. > > Thank you for your help. > > Bernd > > > > partitial output of "multipathd show config" > .... > device { > vendor "EMC" > product "Invista" > product_blacklist "LUNZ" > path_grouping_policy group_by_serial > getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n" > path_selector "round-robin 0" > path_checker tur > features "0" > hardware_handler "1 emc" > prio emc > rr_weight uniform > no_path_retry fail > rr_min_io 1000 > rr_min_io_rq 1 > detect_prio yes > } > > -- > dm-devel mailing list > [email protected] > https://www.redhat.com/mailman/listinfo/dm-devel >
-- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
