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In a scale-out NAS environment, the overall network architecture must be configured to maximize the user experience. Many factors contribute to overall network performance. The following sections list some considerations of jumbo frames, link aggregation, and SmartConnect that benefit the user experience on PowerScale systems. For other general design consideration, see the white paper PowerScale Network Design Considerations.
Jumbo frames are Ethernet frames where the maximum transmission unit (MTU) is greater than the standard 1500 bytes and could be up to 9000 bytes. The larger MTU size provides greater efficiency as less overhead and fewer acknowledgments are sent across devices, drastically reducing interrupt load on endpoints. However, this is not applicable to all workloads.
To take advantage of the greater efficiencies, jumbo frames must be enabled end-to-end on all hops between endpoints. Otherwise, the MTU could be lowered through Path MTU Discovery (PMTUD) or packets could be fragmented. The fragmentation and reassembly impacts the CPU performance of each hop, which impacts the overall latency.
Here are some general considerations for MTU settings with different scenarios. While the general assumption is that jumbo frames provide performance advantages for all workloads, it is important to measure results in a lab environment simulating a specific workload to ensure performance enhancements.
For detailed information about how to configure MTU, see the white paper PowerScale Network Design Considerations.
Link aggregation protocol provides methods to combine multiple Ethernet interfaces, forming a single link layer interface, specific to a switch or server. It balances the network traffic leaving the aggregated interfaces.
It is imperative to understand that link aggregation is not a substitute for a higher bandwidth link. Although link aggregation combines multiple interfaces, applying it to multiply bandwidth by the number of interfaces for a single session is incorrect. Link aggregation distributes traffic across links. However, a single session only uses a single physical link to ensure packets are delivered in order without duplication of frames. Thus, the bandwidth for a single client is not increased, but the aggregate bandwidth of all clients increases in an active/active configuration.
Here are some considerations for using link aggregation:
SmartConnect enables client connection load balancing and dynamic failover and failback of client connections across storage nodes to provide optimal utilization of the cluster resources. SmartConnect eliminates the need to install client-side drivers, enabling the IT administrator to easily manage large numbers of clients with confidence. And in the event of a system failure, file system stability and availability are maintained. For more detailed information about SmartConnect, see the white paper PowerScale Network Design Considerations.
Here are some considerations for using SmartConnect with SMB: