Network Switching; Port Buffering Cache; Switching Methodology - HP StoreVirtual 4000 White Paper

Technical white paper | HP StoreVirtual 4000 Storage

Network switching

Network interfaces on HP StoreVirtual 4000 Storage (physical storage nodes as well as HP StoreVirtual VSA) can connect
to industry-standard network switches (adhering to the IEEE 802.3 Ethernet standard). While any compliant Ethernet
switch works, the capabilities and feature set of the switch is key to designing a robust network for storage.
Key design criteria for iSCSI networks should address:
• Performance
• Reliability
• High availability
• Low latency
To address these design criteria, HP recommends selecting switches that supports the following software and hardware
feature:
Software features:
• Jumbo frame support
• Flow control
• Loop detection
• Quality of services
• Link aggregation protocol
• Traffic filtering (access controls)
• Virtual local area networks (VLANs)
• Routing (optional)
• Switch virtualization (optional)

Port buffering cache

For sequential workloads with larger block sizes, it is recommended that the switch has sufficient buffer cache. In these
environments, it is recommended to allocate at least 512 KB of buffer cache per port. For example, if the switch has 48
ports, which are all used for iSCSI, the recommendation is to have at least 24 MB of buffer cache for those ports.

Switching methodology

The advantage of cut-through switching is that the switch can start transmitting an Ethernet frame on a destination
port before it was received in its entirety on a source port—this is in contrast to store and forward switching in which the
switch has to receive the entire frame first before transmitting it to its destination.
When examining only the first few bytes of a frame, which carries the destination media access (MAC) address, it saves a
considerable amount of time to forward the entire frame to its destination port.
Hardware features:
• Non-blocking backplane
• Sufficient port buffering
• Wire-speed throughput
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