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Commentary

IOV - A Different Way To Wire Once

There is much discussion about wire-once strategies. The concept sounds like nirvana for storage administrators and network managers. Don't worry about the backend protocol, just use 10GbE and use the protocol that you need at the time; iSCSI, NAS or FCoE. Wire-once is not without its challenges and a compelling alternative may be I/O Virtualization (IOV).
There is much discussion about wire-once strategies. The concept sounds like nirvana for storage administrators and network managers. Don't worry about the backend protocol, just use 10GbE and use the protocol that you need at the time; iSCSI, NAS or FCoE. Wire-once is not without its challenges and a compelling alternative may be I/O Virtualization (IOV).Wire-once is very dependent on 10Gbps as well as selecting the right cable. As my colleague Howard Marks discusses in his blog on Network Computing "Wire-Once: Strategy or Pipe dream?" there are several cable options to wade through. Another challenge is wire-once, as it is being proposed, does not address the legacy infrastructures and protocols that are in the data center right now. Most IT people are not interested in ripping out infrastructure that is already in place. Any wire-once strategy would be a very slow transition for most data centers.

As we discuss in our article "What is I/O Virtualization" IOV places a single high speed NIC (or two for redundancy) in each server in a rack. That high speed NIC connects via a single cable set to an I/O gateway at the top of rack. Inside of this gateway multiple interface cards are placed that can provide a wide range of functions and support a variety of protocols. In the rack, cables and network interface cards can be consolidated with only a pair of NICs required in the server and a pair of cables coming out from each server. Today the connections from the server to the I/O gateway can be either Infiniband, PCIe or 10GbE, depending on the vendor.

IOV brings a lot of advantages to managing an infrastructure, cards can be allocated to servers via software without having to interact with a particular server and making sure that a new and correct cable set is run to that server. It also may eliminate the need of having multiple redundant NICs for each type of card in every server, instead something like a global spare NIC can be placed in the I/O gateway. If a NIC in the I/O gateway fails the global spare NIC can take its place.

Most important though IOV does can provide rack simplification without having to put in an entirely new infrastructure. The old NICs are moved to the I/O gateway and connections to storage and the network is made from there. As faster technologies become available and affordable, install them in the I/O gateway. No special cables need to be run to the servers in the rack. If you guess wrong on the cabling or need a faster IOV NIC in the racked servers then you just have to upgrade that one segment not the whole infrastructure.

I/O Virtualization, like other forms of virtualization, abstracts you from the physical management of the storage and IP network. As a result it provides the same advantages that other virtualization strategies do with the potential to further drive down cost and increase flexibility.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.

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