Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.112.0P1 - Page 351

• Intermediate system to intermediate system Software Resiliency During normal operations, Dell Networking OS monitors the health of both hardware and software components in the background to identify potential failures, even before these failures manifest. Software Component Health Monitoring On each of the line cards and the stack unit, there are a number of software components. Dell Networking OS performs a periodic health check on each of these components by querying the status of a flag, which the corresponding component resets within a specified time. If any health checks on the stack unit fail, the Dell Networking OS fails over to standby stack unit. If any health checks on a line card fail, Dell Networking OS resets the card to bring it back to the correct state. System Health Monitoring Dell Networking OS also monitors the overall health of the system. Key parameters such as CPU utilization, free memory, and error counters (for example, CRC failures and packet loss) are measured, and after exceeding a threshold can be used to initiate recovery mechanism. Failure and Event Logging Dell Networking systems provide multiple options for logging failures and events. Trace Log Developers interlace messages with software code to track the execution of a program. These messages are called trace messages and are primarily used for debugging and to provide lower-level information then event messages, which system administrators primarily use. Dell Networking OS retains executed trace messages for hardware and software and stores them in files (logs) on the internal flash. • NV Trace Log - contains line card bootup trace messages that Dell Networking OS never overwrites and is stored in internal flash under the directory NVTRACE_LOG_DIR. • Trace Log - contains trace messages related to software and hardware events, state, and errors. Trace Logs are stored in internal flash under the directory TRACE_LOG_DIR. • Crash Log - contains trace messages related to IPC and IRC timeouts and task crashes on line cards and is stored under the directory CRASH_LOG_DIR. For more information about trace logs and configuration options, refer to S-Series Debugging and Diagnostics. Core Dumps A core dump is the contents of RAM a program uses at the time of a software exception and is used to identify the cause of the exception. There are two types of core dumps: application and kernel. • Application core dump is the contents of the memory allocated to a failed application at the time of an exception. • Kernel core dump is the central component of an operating system that manages system processors and memory allocation and makes these facilities available to applications. A kernel core dump is the contents of the memory in use by the kernel at the time of an exception. High Availability (HA) 351