I’m having big time in understanding PSA, so to make it simple I’m breaking it into as simpler statement as possible
What is NMP?
NMP stands for Native Multipathing Plug-in.
What NMP does ?
NMP is handles MPIO (Multi Pathing Input Output). NMP detects the array type assigns SATP to it.
What is SATP?
SATP stands for Storage Array Type Plug-in.
What SATP does?
SATP decides how to react to path failure based on the storage. It also contains array specific actions or rules to follow when path fails or when specific action is needed.
SATP being a plug-in ships with all standard Arrays information.
It also include information for array which are not generally recognized under
generic array type.
SCSI queries a Array, which returns Array ID. Based on array ID, storage type
is detected by NMP and specific SATP is applied.
Read SATP as a template for specific array type, which has guidelines defined as what to when.
What is PSP?
PSP stands for Path Selection Policy
PSP actually handles path. NMP is car, SATP is road type and PSP is actual Road.
By default NMP assigns one of three PSP
- Round Robin: Remember round robin is same as load balancing done for traffic originating from port id. It is simple dumb, will keep moving I/O’s in and out irrespective of current I/O queue for that specific path. If you wish to add intelligence, add PowerPath VE