Technical data

Solution Architectural Overview
VMware Horizon View 5.3 and VMware vSphere for up to 2,000 Virtual
Desktops Enabled by Brocade Network Fabrics, EMC VNX, and EMC Next-
Generation Backup
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All flows with the same hash traverse the same link, regardless of the total
number of links in a LAG. This might result in some links within a LAG, such
as those carrying flows to a storage target, being over utilized and packets
being dropped, while other links in the LAG remain underutilized. Instead
of LAG-based switch interconnects, Brocade VCS Ethernet fabrics
automatically form ISL trunks when multiple connections are added
between two Brocade VDX® switches. Simply adding another cable
increases bandwidth, providing linear scalability of switch-to-switch traffic,
and this does not require any configuration on the switch. In addition, ISL
trunks use a frame-by-frame load balancing technique, which evenly
balances traffic across all members of the ISL trunk group.
A standard link-state routing protocol that runs at Layer 2 determines if
there are Equal-Cost Multipaths (ECMPs) between RBridges in an Ethernet
fabric and load balances the traffic to make use of all available ECMPs. If
a neighbor switch is reachable via several interfaces with different
bandwidths, all of them are treated as “equal-cost” paths. While it is
possible to set the link cost based on the link speed, such an algorithm
complicates the operation of the fabric. Simplicity is a key value of
Brocade VCS Fabric technology, so an implementation is chosen in the
test case that does not consider the bandwidth of the interface when
selecting equal-cost paths. This is a key feature needed to expand
network capacity, to keep ahead of customer bandwidth requirements.
Pause Flow Control is enabled on vLAG-facing interfaces connected to
the ESXi hosts, and the NFS server. Brocade VDX Series switches support
the Pause Flow Control feature. IEEE 802.3x Ethernet pause and Ethernet
Priority-Based Flow Control (PFC) are used to prevent dropped frames by
slowing traffic at the source end of a link. When a port on a switch or host
is not ready to receive more traffic from the source, perhaps due to
congestion, it sends pause frames to the source to pause the traffic flow.
When the congestion is cleared, the port stops requesting the source to
pause traffic flow, and traffic resumes without any frame drop. When
Ethernet pause is enabled, pause frames are sent to the traffic source.
Similarly, when PFC is enabled, there is no frame drop; pause frames are
sent to the source switch.
VLANs isolate network traffic to allow the traffic between hosts and
storage, hosts and clients, and management traffic to move over isolated
networks. In some cases, physical isolation may be required for regulatory
or policy compliance reasons; in many cases, logical isolation using VLANs
is sufficient. This solution calls for a minimum of three VLANs:
 Client access
 Storage
 Management
Figure 20 illustrates the VLANs.
Equal-Cost
Multipath
(ECMP)
Pause Flow
Control
VLAN