Practical Cloud Knowledge: Install, Configure, and Manage - Deploying and Managing a Cloud Infrastructure - page 213

Managing large pools of resources has historically been a complicated and expensive pro-
cess, and often single points of failure can bring an entire system down, requiring more time
and expense to get it back up. The answer to this problem is distributed storage clustering,
which brings the following benefits:

Easy management through multiple master controllers

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Failure tolerance because failure in some areas cannot take down the whole grid

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Scalability of capacity, performance, and availability through small and modular
increments

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Higher utilization rates due to better administration

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Lower hardware cost because upgrades can be done in small batches at a time com-
pared to building new data centers every time a new pool of resources is required

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N_Port ID Virtualization
N_Port ID Virtualization (NPIV) is a new Fibre Channel facility that allows multiple
worldwide names for ports and nodes to be assigned to a single N_Port, which can be a
physical Fibre Channel host bus adapter (HBA) in a server or a target port on a storage
array. This is in the context of storage area networks (SANs), logical unit numbers (LUNs),
and virtual machines.
Normally, an N_Port will have a single N_Port_ID associated with it. This is not the
same as the World Wide Port Name (WWPN), but their relationship is typically one-to-
one, which means that every N_Port can have only one N_Port_ID and one WWPN. What
NPIV does is allow one N_Port to have multiple IDs and hence multiple WWPNs as well.
To get an idea of why this is useful, consider a virtualized environment where you have
multiple virtual machines and a LUN or a SAN that you want to be available to only specific
virtual machines through a Fibre Channel. If you didn't use NPIV, the N_Port on the host
would have only a single WWPN and ID. LUNs then would have to be zoned and presented
to this single WWPN assigned to the single N_Port, but because all the virtual machines
would be sharing this single N_Port, the same ID, and the same WWPN, all of them would
be able to access the LUN when you want only a few specific ones to have access to it.
Using NPIV, you can now assign multiple N_Port_IDs and multiple WWPNs to the
single physical N_Port you have on the host. When you register additional WWPNs, each
virtual machine can have its own WWPN, so when you build SAN zones and present
LUNs to virtual machines using the specific WWPN assigned to those VMSs, the LUNs
will be accessible to only those specific VMs and not the others.