Storage Area Networks For Dummies®

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Par t II: Designing and Building a SAN
You’ll also find load balancing and path fail-over software for the Windows
server platform. Check with your storage array vendor on how to go about
configuring it, because it differs depending on the vendor.
When dealing with multiple paths on Windows, I usually recommend that
you create your file system on only the first instance of your new disk in
Disk Administrator. The rest of the copies are just the second instance, third
instance, and so on of the first — so you don’t want to do things twice, three
times, or as many times as there are copies.
iSCSI, You SCSI, We All SCSI
The iSCSI protocol runs on top of standard Ethernet TCP/IP networks, so you
may already have all the cables and network switches you need to use it for
your SAN. You might even have 10 gigabit-per-second LAN links, which are
even faster than today’s 8 gigabit-per-second limit for Fibre Channel.
Because iSCSI uses traditional Ethernet networks to communicate, it is
quickly becoming a more prevalent way to connect storage arrays with servers.
Although not everyone has Fibre Channel cabling in their datacenter,
just about everyone has an Ethernet network. Using what you already have
is always quicker, cheaper and easier. However, many users who implement
larger iSCSI solutions prefer to build a dedicated network for the storage traffic,
just to keep it more secure and easier to troubleshoot. For the purpose
of explanation, I’ll put iSCSI on its own network to show you everything from
the ground up. That doesn’t mean you can’t put it on an existing Ethernet
network. It’s up to you and your network folks to decide whether you have
the room to add that traffic on top of your existing LAN traffic.
Before you start plugging in new stuff, you should make sure you understand
the basic iSCSI terminology.
Initiators and targets
In iSCSI, it is important not to confuse an initiator and a target. An initiator is
the device that initiates the conversation between your host computer and a
storage device. (Instead of using specialized Fibre Channel HBAs, your host
initiates a conversation between one of its regular Ethernet LAN ports and
another device on the same network.) A target is an Ethernet LAN port on the
network which is on the iSCSI storage array. (Target ports are where LUNs
from the storage array will be assigned to initiators.)