Information Technology Reference
In-Depth Information
dropped frames, and ensure that you have “bet-the-business” Ethernet infrastructure when
using iSCSI.
Figure 6.12
Using iSCSI, SCSI
control and data
are encapsulated
in both TCP/IP and
Ethernet frames.
Ethernet
frame
IP
packet
TCP
packet
iSCSI payload data unit (PDU)
Although Fibre Channel is often viewed as having higher performance than iSCSI, in many
cases iSCSI can more than meet the requirements for many customers, and a carefully planned
and scaled-up iSCSI infrastructure can, for the most part, match the performance of a moderate
Fibre Channel SAN.
Also, iSCSI and Fibre Channel SANs are roughly comparable in complexity and share many
of the same core concepts. Arguably, getting the i rst iSCSI LUN visible to an ESXi host is sim-
pler than getting the i rst Fibre Channel LUN visible for people with expertise with Ethernet
but not Fibre Channel because understanding worldwide names and zoning is not needed. In
practice, designing a scalable, robust iSCSI network requires the same degree of diligence that is
applied to Fibre Channel. You should use VLAN (or physical) isolation techniques similarly to
Fibre Channel zoning, and you need to scale up connections to achieve comparable bandwidth.
Look at Figure 6.13, and compare it to the switched Fibre Channel network diagram in
Figure 6.8.
Figure 6.13
Notice how the
topology of an iSCSI
SAN is the same as
a switched Fibre
Channel SAN.
ESXi host
ESXi host
ESXi host
Each ESXi host has
a minimum of two
vmkernel ports, and
each is physically
connected to two
Ethernet switches.
Storage and LAN
are isolated—
physically or via
VLANs.
FC switch
FC switch
Each switch has a
minimum of two
connections to two
redundant front-end
array ports (across
storage processors).
VMFs
datastore
iSCSI
array
iSCSI
LUN
Each ESXi host has a minimum of two VMkernel ports, and each is physically connected to
two Ethernet switches. (Recall from Chapter 5, “Creating and Coni guring Virtual Networks,”
that VMkernel ports are used by the hypervisor for network trafi c such as IP-based storage
trafi c, like iSCSI or NFS.) Storage and LAN are isolated—physically or via VLANs. Each switch
