Chapter 2 - 7. Understanding Congestion in Fibre Channel Fabrics

The Culprit Host

In this case, is Host-1 really a culprit? The answer depends on whether to look from Host-1’s perspective or fabric’s perspective. If looking from Host-1’s perspective, calling it a culprit may not be entirely correct because it’s not doing anything it shouldn’t be doing. It connects to the switch at 8GFC and it receives traffic at full capacity. Also, the link between Host-1 and Switch-1/Port-1 is not congested because it has enough credits to send the frames at full capacity. However, if Host-1 was initiating several large read I/O operations to multiple targets closely spaced together then perhaps the case could be made that the host is requesting more data than it possibly could receive on its 8GFC link. It’s the responsibility of a device to control how much traffic it sends or receives. In this case, the device is asking for more data than can be sent on its directly connected link. Because of this reason, calling Host-1 a culprit is justified. 在这种情况下，Host-1 真的是罪魁祸首吗？答案取决于是从 Host-1 的角度还是从Fabric的角度来看。如果从主机-1 的角度来看，称其为罪魁祸首可能并不完全正确，因为它并没有做任何不该做的事情。它以 8GFC 连接到交换机，并以满负荷接收流量。此外，Host-1 和 Switch-1/Port-1 之间的链路也没有出现拥塞，因为它有足够的点数来满负荷发送帧。但是，如果主机-1 对多个目标启动了多个大读取 I/O 操作，而且间隔很近，那么主机请求的数据量可能会超过它在 8GFC 链路上可能接收到的数据量。设备有责任控制其发送或接收的流量。在这种情况下，设备请求的数据量超过了其直接连接链路所能发送的数据量。因此，称 Host