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ESXi 5.1 Path Selection Claim Rules

One of my goals for 2014 is to gain a better understanding of how things really work in VMware.
 
Today's question, path selection policies and Claim Rules. Am I correct when I state the following..

A Claim rules specifics that a specific disk type should default / always be associated with a specific PSP correct?

Also, why would anyone want to specific a PSP on a disk instead of at the volume level..

Thanks Again
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compdigit44
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compdigit44
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
The PSA (Pluggable Storage Architecture) uses claim rules to determine with multi pathing modules, to claim which storage devices to apply these rules and plugins.

So inanswer to your question:-

A Claim rules specifics that a specific disk type should default / always be associated with a specific PSP correct?
- Yes this is correct.

Also, why would anyone want to specific a PSP on a disk instead of at the volume level..

If we take an Equallogic LUN from a SAN, for example, the claim rule would identity it's an Equallogic device, and claim the rule, and apply a rule, so it can use a third party Dell plugin to handle multi-pathing for that LUN, e.g. the Dell Equallogic EqualLogic Multipathing Extension Module. (MEM) for VMware® often referred to as the MEM Kit, so custom path selection policy can be used, rather than Round Robin etc to better control Active (I/O) to both LUNs/paths at the same time.

It's quite interesting (if sad like us), if you look at the logs (/var/log/vmkernel.log), and you can see this happening, and the claim rules working in the background.
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compdigit44Author Commented:
Thanks Hancock!!!!
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
No problems.
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