Chapter 4-11. Troubleshooting Congestion in Fibre Channel Fabrics

The OBFL Commands—show logging onboard

The On Board Failure Logging (OBFL) is a feature on Cisco MDS switches that stores important metrics and logs with time and date stamps. The following are more details about OBFL. 板载故障日志（OBFL）是 Cisco MDS 交换机上的一项功能，用于存储带有时间和日期戳记的重要指标和日志。以下是有关 OBFL 的详细信息。

1. Each module on modular platforms (MDS 9700 Directors) has a dedicated OBFL, whereas the fixed fabric switches maintain a per-switch OBFL. 模块化平台（MDS 9700 Director）上的每个模块都有专用的 OBFL，而固定结构交换机则维持每个交换机的 OBFL。

2. MDS switches maintain OBFL in Non-Volatile Random Access Memory (NVRAM), which is persistent memory. As a result, OBFL logs are not lost even if the module or switch is restarted, reloaded, or power cycled. MDS 交换机将 OBFL 保存在非易失性随机存取存储器 (NVRAM) 中，这是一种持久性存储器。因此，即使模块或交换机重新启动、重新加载或电源循环，OBFL 日志也不会丢失。

3. There are several event types in OBFL and each has its own fixed-size cyclical file. Once it fills up, the oldest entry, chronologically, is overwritten with the newest entry. This is called cyclical file wrapping. OBFL 有几种事件类型，每种类型都有自己固定大小的循环文件。一旦文件填满，按时间顺序排列的最旧条目就会被最新条目覆盖。这就是所谓的循环文件包装。

4. There is no need to clear the OBFL entries. We don’t even recommend doing this because clearing the entries may lead to loss of information, as seen in Case Study 1. Clearing