pp_alua

This prioritizer uses the SCSI-feature called Asymmetric Logical Unit Access to determine the ALUA state of a device.

pp_balance units

This path prioritizer aims to balance logical units over all controllers available. The logic followed by the pp_balance_units prioritizer is:

• list all paths in all primary path groups
• for each path, get the controller's serial
• compute the number of active paths attached to each controller
• compute the max number of paths attached to the same controller
• if sums are already balanced or if the path passed as parameter is attached to controller with less active paths, then return (max_path_attached_to_one_controler - number_of_paths_on_this_controler)
• else, or if anything goes wrong, return 1 as a default prio

pp_random

Does what it says, returns random priority values.

pp_emc

Vendor path prioritizer for EMC Clariion.

pp_hds_modular

Vendor path prioritizer for Hitachi modular (DF) and enterprise SAN (OPEN-). This prioritizer prioritizes pathes of even LDEV's (internal LUN's) to even storage controllers and pathes of odd LDEV's to odd storage controllers. It enables a static load-balancing for HDS modular storage class. Dynamic load-balancing does not make sense with modular storage class subsystems. Note: pp_hds_modular is not yet part of the released multipath-tools package.