Administrator Guide

Software Resiliency
During normal operations, Dell EMC 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 EMC 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 EMC Networking OS fails over to standby stack unit. If any health checks on a line card
fail, Dell EMC Networking OS resets the card to bring it back to the correct state.
System Health Monitoring
Dell EMC 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 EMC 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 EMC 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 EMC 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.
System Log
Event messages provide system administrators diagnostics and auditing information.
Dell EMC Networking OS sends event messages to the internal buffer, all terminal lines, the console, and optionally to a syslog server. For
more information about event messages and configurable options, refer to Management.
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High Availability (HA)