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VMware vSphere Distributed Switches centralize virtual switch management, creating structure and organization to help simplify network administration. VSphere Distributed Switches also offer users the capability to closely monitor and manage network traffic in order to assign adequate amounts of bandwidth to servers and optimize network use.
How is network traffic managed through vSphere Distributed Switches?
VSphere Distributed Switch instances employ two technologies to manage network traffic: network I/O control (NIOC) and traffic shaping.
NIOC embraces the notion of bandwidth priority and allocation to establish quality of service (QoS) for network traffic. The idea is to represent bandwidth as a resource pool divided into 100 equal shares, like a percentage. Then, each major network traffic type -- such as vMotion, storage area networks, ordinary VM instance traffic, custom types and so on -- are identified and assigned some number of those shares. The portion of bandwidth assigned to each traffic type illustrates the relative importance of each traffic type -- and guarantees bandwidth for that traffic to maintain QoS.
NIOC prevents one type of traffic from overwhelming other traffic types and possibly affecting the performance of other traffic. For example, a vMotion event might demand significant bandwidth and reduce the performance of other VMs passing ordinary data across the network. But suppose, for example, vMotion traffic is assigned 10 shares, while VM traffic is given 50 shares under NIOC. This means vMotion traffic has a lower priority and will only receive limited bandwidth when other traffic is present. This not only guarantees minimum bandwidth, but enforces bandwidth limits. Remember, NIOC only affects outbound traffic leaving the ESXi host. NIOC is more meaningful when faster network infrastructures are available, such as 10 Gigabit Ethernet or faster.
Part one: VSphere Distributed Switches add robust network features and aggregate VSphere Standard Switch deployments to simplify networking.
Part two: VSphere versions 5 and 6 bring powerful improvements to the VMware vSphere Distributed Switch for better network management.
Part three: Updating vDS to the latest version of vSphere is a nondisruptive process and can be accomplished without taking hosts or VMs offline.
Bidirectional traffic shaping is an additional configuration feature for inbound and outbound network traffic, which can be used in conjunction with NIOC. Shaping can be applied at the distributed virtual port and distributed virtual port group level, allowing more granular control of network traffic priorities based on average bandwidth, peak bandwidth and burst size.
However, traffic shaping must be configured with extreme caution. It is most beneficial when the physical or virtual switch infrastructure is oversubscribed -- or utilized beyond normal limits -- and the additional traffic shaping can help to prioritize or optimize network use, possibly helping to mitigate performance impairment from traffic competing for limited switch capacity. Networks with ample bandwidth and switch capacity can typically use NIOC alone.
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