Storage Area Networks For Dummies®

Chapter 2: SAN Building Blocks
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Using a dedicated HBA in each server to connect to shared tape storage
through a hub offers several advantages:
✓ Greater efficiency: You can do backups over the SAN while keeping
your backup traffic separate from disk traffic.
✓ Less cost: Hubs are inexpensive, especially in comparison to buying a
backup tape drive for every server. Using a hub to move tape backup
traffic off of a SAN and onto its own separate network could also free up
SAN bandwidth for other production applications.
SAN switches
SAN switches are used as central connection points for the devices in a SAN
that require disk access. You attach a Fibre Channel cable to the GBIC on the
HBA in the server and connect the other end to a GBIC port on a switch. The
storage array gets connected the same way. A switch is, in effect, a bunch of
wires connected together which enables every device on every wire to talk to
any other device at the same time. When a switch can transmit data across all
wires at the same time, it’s known as a non-blocking switch. (See Figure 2-7.)
Figure 2-7:
SAN switch
logic.
Disk
storage
Every port has access to every other port.