Network Latency - HP MPX200 User Manual

For optimal availability and performance, consider the following:
Switch Infrastructure: Dual Redundant 1 or 10 Gigabit switches trunked together for bandwidth
and fault-tolerance.
1 GbE iSCSI blade and 10 GbE iSCSI blade connectivity: at least one port from each blade
connected to each switch.
1 GbE iSCSI blade connectivity: When using 2 GE ports, utilize GE port 1 and GE port 3 or
GE port 2 and GE port 4 for improved performance balancing.
Host Server connectivity: Dual NICs connected to the IP storage network with a single port
connected to each switch. For Windows 2003/2008, use the HP DSM for MPIO for multiple
NIC support.

Network latency

High network latency can be the primary cause of slow I/O performance, or worse, iSCSI drive
disconnects. It is important to keep network latency (for example, ping response time measurement)
on your IP-SAN subnet below 2 milliseconds. Many factors can contribute to increasing network
latency, such as congestion, distance, and router hops. Configuring the IP-SAN on a single IP
subnet with layer-2 switching helps to lower the network latency.
Network bandwidth
Network bandwidth required for an IP-SAN depends on the server applications, maintenance
utilities, and backup/recovery processes. Most I/O intensive applications, like Microsoft Exchange
and SQL Server,do will not consume much network bandwidth and are more sensitive to network
latency issues. Bandwidth becomes much more important when you are performing maintenance
operations, like backup/recovery. Any sequential read/write stream could consume significant
bandwidth.
NOTE: Storage data transfer rates are typically measured in bytes while network data transfer
rates are measured in bits. A 1 Gb/sec network connection can transfer a maximum of 120–130
MB/sec. Microsoft Windows provides performance monitor counters that can help to determine
the data-path bandwidth requirements. Disk Bytes/sec is the rate bytes are transferred to or from
the disk during write or read operations.
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