Recently I was researching some storage related issues and found out this cool feature in @MostafaVMW's recent book on Storage Implementation on vSphere 5.0 about ranking your paths when you are using VMW_PSP_MRU with ALUA arrays or non-ALUA Active/Passive Arrays.
So by using the ranked paths you can (indirectly) actually configured preferred path without using the VMW_PSP_FIXED plugin.
As you can rank the paths in ALUA configuration, if one path is no longer valid then PSP fails back to a path which has a higher rank configured. In non-ALUA it goes by the path Group State which is Active and if not available then goes by Standby state.
You can use the following command to setup the rank which goes in the way like "Higher the value and higher the rank for that path" (Default is 0 - Zero).
esxcli storage nmp psp generic pathconfig set -c "rank-" -p
You can get the existing ranking for the path using the command:
esxcli storage nmp psp generic pathconfig get –p
Note: Where XX needs to be replaced by numeric value and path name should be provided depending on your requirement/s. Path names can be runtime path name or physical path name.
So to summarize if an AO path with highest rank fails , it will find the next path with highest rank and fails over to that path, but suppose there is no other AO path available with any ranking, then it will fail over to the next highest ranked path which is connected to a port in ANO state and eventually in standby state.
vSphere Client does not have the functionality at present to setup the ranking for the paths so you need to use esxcli command line only for now.
Hope you can use this feature in certain conditions where multipathing policies are not fully available but you can still benefit out of the existing setup using this feature.
I am just spreading the information for those who does not have access to the book. At the same time indeed suggesting to everyone to buy it and read it for further/deeper understanding of all the vSphere Storage related concepts.
Thanks and please share !!
So by using the ranked paths you can (indirectly) actually configured preferred path without using the VMW_PSP_FIXED plugin.
As you can rank the paths in ALUA configuration, if one path is no longer valid then PSP fails back to a path which has a higher rank configured. In non-ALUA it goes by the path Group State which is Active and if not available then goes by Standby state.
You can use the following command to setup the rank which goes in the way like "Higher the value and higher the rank for that path" (Default is 0 - Zero).
esxcli storage nmp psp generic pathconfig set -c "rank-
You can get the existing ranking for the path using the command:
esxcli storage nmp psp generic pathconfig get –p
Note: Where XX needs to be replaced by numeric value and path name should be provided depending on your requirement/s. Path names can be runtime path name or physical path name.
So to summarize if an AO path with highest rank fails , it will find the next path with highest rank and fails over to that path, but suppose there is no other AO path available with any ranking, then it will fail over to the next highest ranked path which is connected to a port in ANO state and eventually in standby state.
vSphere Client does not have the functionality at present to setup the ranking for the paths so you need to use esxcli command line only for now.
Hope you can use this feature in certain conditions where multipathing policies are not fully available but you can still benefit out of the existing setup using this feature.
I am just spreading the information for those who does not have access to the book. At the same time indeed suggesting to everyone to buy it and read it for further/deeper understanding of all the vSphere Storage related concepts.
Thanks and please share !!
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