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The Case For I/O Virtualization

When the term "virtualization" is used, the implicit assumption is that we're talking about "server virtualization." But other types of virtualization exist, such as storage virtualization. And now I/O (input/output) virtualization is starting to encroach upon our consciousness.

Just what is I/O virtualization?  Answering that question requires a brief review of the role of I/O in a system. The job of a computer is to perform "data processing." A CPU processes data from its associated transient memory, but the data typically has to be acquired from storage somewhere, and a network is used to link the two. The movement of data is all about I/Os (inputs are reads from storage to a server and outputs are writes to storage).

To be clear, the use of network may be grandiose when using direct attached storage where a bus or I/O interconnect is sufficient rather than a LAN or SAN, but logically any connectivity is still part of a network.

Now if I/O needs to get in or out of the server chassis box in conjunction with an external network composed of such things as cables and switches, an I/O adapter is necessary to connect and translate network protocols to the CPU/memory complex of a server. If the network is a SAN, a Fibre Channel HBA (host bus adapter) may be the I/O adapter. Or, if the connection is to a LAN or WAN, an Ethernet NIC (network interface card) may be used. However, the I/O adapter is located within the server box.

What I/O virtualization does is move these adapters from the server box to a new box called an I/O virtualization switch box that is external to the server. VirtenSys is joining the I/O virtualization party (where NextIO has played for over a year) by providing such a switch. With the VirtenSys solution, a single PCIe cable connection is made between each physical server and the I/O virtualization switch. Each server no longer has a dedicated I/O adapter, but rather has virtual I/O connectivity through non-dedicated access to I/O adapter resources on the I/O virtualization switch.

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