HP Storevirtual 4000 - Network Switching; Port Buffering Cache; Switching Methodology

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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
• Trac ltering (access controls)
• Virtual local area networks (VLANs)
• Routing (optional)
• Switch virtualization (optional)
Hardware features:
• Non-blocking backplane
• Sucient port buering
• Wire-speed throughput
Port buering cache
For sequential workloads with larger block sizes, it is recommended that the switch has sucient buer cache. In these
environments, it is recommended to allocate at least 512 KB of buer 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 buer 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 rst before transmitting it to its destination.
When examining only the rst 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.