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.
@30651 On closer inspection, SAN segmentation is about logically
separating different fabrics. That is, you can connect multiple
Fibre Channel (FC) fabrics together, yet
have them logically isolated to maintain their own autonomy and
namespaces, and not have to worry about management traffic
crossing the different fabrics. This is very similar to the way
you would segment a LAN. Another form of routing deals with
distance, which has traditionally been known as "channel
extension" in the mainframe world. For example, you see storage
over
IP, FCIP or other technologies that enable
storage to be moved over long distances for remote tasks like
mirroring,
replication, copy,
backup and so on. Yet another form of
routing is protocol conversion, such as FC to iSCSI or iSCSI to
FC -- mapping a protocol across different interfaces allowing
traffic to be bridged or routed across different networks.
Consequently, you'll hear terms like router, gateway, bridge,
etc. but they are all routing traffic between network segments,
routing protocols across different interfaces or routing data
over long distances across the same (or different) networks.
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.
Listen to the
SAN FAQ audiocast here.
Go back to the beginning of the
Storage Area Network FAQ Guide.