ALUA is an acronym that stands for "Asymmetric Logical Unit Access". For SANs, typically there are many paths from your servers to your storage - this is OK because you don't want any single point of failure. However, it's a problem if you have two storage controllers/servers that can access the same disk/LUN. Without ALUA your servers might take a non-optimal path to get to the LUNS.
ALUA was designed to solve this problem by making the client/initiator aware of the different paths, and to automatically choose the optimal path (AKA "Primary" path in the illustration above). The non-optimal/non-primary paths will still be available, but will only be used if the primary path becomes unavailable. If you aren't using ALUA and your hosts are using non-optimal paths, you may experience increased latency / reduced performance
Enabling ALUA
ALUA was designed to solve this problem by making the client/initiator aware of the different paths, and to automatically choose the optimal path (AKA "Primary" path in the illustration above). The non-optimal/non-primary paths will still be available, but will only be used if the primary path becomes unavailable. If you aren't using ALUA and your hosts are using non-optimal paths, you may experience increased latency / reduced performance
Enabling ALUA
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