Optimizing-QoS-vSphere_final

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Using dual-port 10GbE server adapters
helpsmakeoptimaluseofPCIe
motherboard slots, allowing for future
expansion. Therefore, when available
PCIeconnectivityonthemotherboard
permits it, dual-port server adapters are
preferable to single-port ones.
To provide near-native 10 Gbps
throughput, it is necessary to ensure that
thereisenoughPCIebandwidthavailable
totheadapterorLAN-on-Motherboard
connection.WithregardtoPCIe
requirements, one must consider both
speed(forexample,PCIeGen1orPCIe
Gen 2) and channel width (for example,
x4orx8).TheminimumPCIerequirements
for one-port and two-port server
adapters are as follows:
•
requirePCIeGen1x8orPCIeGen2
x4 connections
•
requirePCIeGen2x8connections
Whiletwo-portPCIeGen1adaptersare
available, it is important to note that the
maximum unidirectional bandwidth of
about 12 Gbps is shared between the
two ports. Most of the Gen 1 adapters
were released prior to Gen 2 being
widely available and were the only
option. Further, the size of a physical
PCIeconnectorisnotnecessarilyan
accurate indication of channel width. For
example, an x8 physical connector on
a motherboard may provide only x4 or
even x1 connectivity. Refer to the server
documentation to verify the proper
adapter placement.
Testing shows a bidirectional limit of
approximately25Gbpswhenusinga
dual-portadapteronaPCIeGen1
connection.PCIeGen2canprovide
enough bandwidth for a dual-port 10GbE
adapter, and when used in conjunction
with NetQueue, near-native throughput
is possible. Testing shows greater than
30Gbpsofbidirectionaltrafcacrossa
two-port10GbEadapterusingaPCIeGen2
connection and larger buffer size,
as shown in Figure 1.
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The maximum
bandwidth that ESX* can use will continue
to increase as newer and more powerful
server platforms become available, making
this an important best practice going
forward.AlsonotethatwhilePCIeGen
3 will be available on servers by the end
of 2011, the additional bandwidth is not
needed on dual-port 10GbE controllers for
full bidirectional
line rate.
QoS Best Practice 2: Use VMware


VMware supports NetQueue, a
performancetechnologythatsignicantly
improves performance in 10GbE
virtualized environments by aligning and
spreadingthenetworkI/Oprocessing
across multiple processor cores. Even
with today’s high performance servers
and hypervisor improvements, it can
bedifculttoachievenear-native
performance without spreading the load
across multiple cores. While NetQueue is
enabled by default in ESX versions 4.0
and 4.1, when using Ethernet controllers
that support NetQueue, the following
procedure can be used to verify that it is
enabled.
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NetQueue* is enabled in the VMkernel using the Advanced Settings dialogue box.
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