SCSI Logging Level
The scsi_logging_level command, typically part of the sg3-utils package, is a powerful tool for configuring and monitoring the logging behavior of the Linux SCSI stack. It allows administrators and developers to fine-tune the verbosity of SCSI-related kernel messages, aiding in debugging, performance analysis, and understanding device interactions.
Understanding SCSI Logging Levels
By adjusting logging levels, you can gain deeper insights into the SCSI command flow, from submission to completion. This is crucial for diagnosing issues related to storage devices, controllers, and the underlying kernel drivers.
Configuring SCSI Tracepoints
The scsi_logging_level command enables you to set specific tracepoints within the SCSI subsystem. This provides granular control over what information is logged, helping to reduce noise and focus on relevant events.
Setting SCSI IOCTL Logging
To configure the log level for various tracepoints along the Linux SCSI stack, you can use the -s --ioctl option. For instance, setting the level to 7 provides a comprehensive view of IOCTL operations:
# scsi_logging_level -s --ioctl=7Tracking SCSI Command Flow
To monitor SCSI commands as they traverse the submission and completion paths, use the -s --midlevel option. This is particularly useful for observing the lifecycle of commands. After setting this level, it's recommended to check the kernel message log (e.g., using dmesg) for the captured information:
# scsi_logging_level -s --midlevel=7Benefits of Using scsi_logging_level
- Enhanced Debugging: Pinpoint issues within the SCSI subsystem more effectively.
- Performance Insights: Analyze command latency and identify bottlenecks.
- System Understanding: Gain a clearer picture of how storage devices interact with the kernel.
- Reduced Log Noise: Focus logging on specific areas of interest.