After you've defined targets, use the Targets
tab to select and log on to the proxied iSCSI
targets. As Figure 4 shows, the logon window
also enables you to select whether a target is
persistent and whether multipathing is used
for this connection. Click Advanced in the
logon window to configure cyclical redundancy check (CRC), CHAP, and IPsec settings
for this connection.
Once the logon session between the iSCSI
initiator and proxied iSCSI target is active, you
can configure the iSCSI storage volume via the
Windows Disk Management utility, assign it a
drive letter, and format it for use.
A Dedicated IP SAN
Compared with a messaging LAN (i.e., a LAN
that carries application traffic as opposed to
storage traffic), a Fibre Channel SAN is inherently a separate network, with its own cabling
scheme, protocols, and fabric infrastructure.
If properly designed, congestion on a Fibre
Channel SAN should be minimal and high
availability is enhanced through redundant
pathing between initiators and targets.
One of the more marketed aspects of
iSCSI is that it can be run over common
LAN infrastructures by using relatively cheap
Gigabit Ethernet switches. This means that
storage and messaging traffic coexists on the
same LAN. Certainly there are no significant
technical barriers to prevent this. However,
Microsoft and, in particular, storage vendors
typically advise against combining storage
and messaging traffic on the same network.
Messaging traffic can withstand wide fluctuations in latency, congestion, and packet
loss and recovery; storage traffic can't. Consequently, the Ethernet network between
the iSCSI gateway and the complex of iSCSI
initiators it's serving should be a dedicated IP
SAN, as Figure 5 shows.
Designing a dedicated IP SAN from the
start takes advantage of more low-cost perserver connection and use of commodity
Gigabit Ethernet switches, and it allows you to
scale the IP SAN over time to accommodate additional servers-without significantly impacting (or being-impacted by) the corporate LAN.
iSCSI is now a mature storage technology and is being deployed for small
departmental operations as well as data
center applications. Today, Fibre Channel
is still the transport of
choice for many data
centers with high
bandwidth and high
availability requirements. Combining
iSCSI and Fibre Channel SAN technologies
helps administrators bring all server assets into
a common storage infrastructure and provide
best practices handling of all corporate data.
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