Road Thrashing Circumstance dos

Figure 6.3 shows a variation on Scenario 1 in which the Fibre Channel fabric was designed according to VMware best practices. This by itself wouldn’t result in path thrashing. However, the designer decided to customize each host so that they have different preferred paths to LUN 1. These preferred path settings are represented by the interrupted lines (a path from Host A and another path from Host B). The expected behavior in this configuration is that as long as the defined preferred path to LUN 1 is available, the host insists on sending I/O via that path. As a result, Host A attempts to send its I/O to LUN 1 via SPA, and Host B sends it I/O via SPB. However, LUN 1 is owned by SPA and attempts to send I/O via SPB, resulting in a check condition with the sense key ILLEGAL_Request (more on this in Chapter 7). Diesen Beitrag weiterlesen »