Some folks see storage area network (SAN) routing as just segmentation; some see it as protocol conversion; some see it as distance enablement. SAN routing really embraces all those -- and even more functionality.
Virtualization is a bit more nebulous. It can mean volume management, LUN pooling, LUN management, mirroring, replication, snapshots/point-in-time copies, transparent data migration and other functions that would normally be handled through a volume manager or within a storage system or storage array itself. A point of confusion about virtualization is that different vendors' products can often do different things. For example, the Brocade Communications Sytems Inc. Multiprotocol Router AP7420 (MPR can convert protocols (e.g., iSCSI to FC) and can also host storage virtualization applications, such as EMC Corp. Invista and Fujitsu virtualization platform. Another popular device is the Cisco Systems Inc. Storage Services Module (SSM) blade. The software that you run on it will define the device's suite of capabilities. When a vendor first introduces a blade or other module, it's important to determine the software that will run on it.
Some solutions specialize. For example, QLogic Corp., Sanrad Inc. and others make purpose-built appliances that only do protocol conversion or SAN extension -- often with some level of volume management. Those are particularly attractive when keeping acquisition and deployment costs down while tackling specific tasks. Then, you have the multiprotocol or multifunction type devices like the Cisco and Brocade modules that can do a variety of things depending on the software you choose to deploy on them. Today, vendors frequently offer tiers of functionality to meet each organization's needs. That's great because now you can match the notion of tiered storage with tiered connectivity -- applying the right technology to the task at hand without wasting money or functionality.
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