Chapter 8 - 9. Congestion Management in TCP Storage Networks

Estimating I/O Flow Performance from TCP Flow Performance

As mentioned earlier, at the time of this writing, performance monitoring of I/O flows is not available in Ethernet switches. However, some switches (such as Cisco Nexus 9000) can monitor the performance of TCP flows. Based on the TCP port numbers and the direction of high throughput flows, I/O performance can be estimated. 如前所述，在撰写本文时，以太网交换机还不能对 I/O 流量进行性能监控。不过，有些交换机（如 Cisco Nexus 9000）可以监控 TCP 流量的性能。根据 TCP 端口号和高吞吐量流量的方向，可以估算出 I/O 性能。

Remember that with iSCSI and NVMe/TCP, generally the host/initiator initiates a TCP connection to the target/controller for carrying I/O operations. As a result, packets with destination TCP port numbers 3260 (for iSCSI) and 4420 (for NVMe/TCP) are destined for the target/controller. Likewise, packets with source TCP port numbers 3260 (for iSCSI) and 4420 (for NVMe/TCP) are destined for the host/initiator. Because network switches may not inspect the traffic any further than layer 4, it is not possible to find if the packet belongs to a read or a write I/O operation because this information is available only with the header of the upper layer protocols. This issue can be solved by using the port numbers in the TCP header to find the destination of the traffic and analyzing the throughput per TCP flow (different from I/O flow) as explained in the earlier section on Correlating I/O Operations, Traffic Patterns, and Network Congestion. 请记住，对于 iSCSI 和 NVMe/TCP，主机/启动器通常会启动与目标/控制器的 TCP 连接，以执行 I/O 操作。因此，目标 TCP 端口号为 3260（对于 iSCSI）和 4420（对于 NVMe/TCP）的数据包都是以目标/控制器为目的地。同样，源 TCP 端口号为 3260（用于 iSCSI）和 4420（用于 NVMe/TCP）的数据包的目的地是主机/启动器。由于网络交换机对流量的检查可能不会深入到第 4 层，因此无法确定数据包属于读取还是写入 I/O 操作，因为只有上层协议的报头才能提供这一信息。要解决这个问题，可以使用 TCP 报头中的端口号来查找流量的目的