fio:tldr:3173d

This command is using the "fio" tool with elevated privileges (using "sudo").

Here is the breakdown of the command with explanations for each option:

• --filename=${filename}: Specifies the filename or device to be used for the I/O operations. ${filename} is a placeholder that should be replaced with the actual filename or device.
• --direct=1: Enables direct I/O, bypassing the kernel page cache.
• --rw=read: Sets the I/O access pattern to "read", indicating that the command will perform read operations.
• --bs=4k: Specifies the block size of I/O operations, where 4k represents 4 kilobytes.
• --ioengine=libaio: Selects the I/O engine to be used, in this case, "libaio" (asynchronous I/O).
• --iodepth=256: Sets the I/O depth, which determines the number of outstanding I/O operations at a given time.
• --runtime=120: Specifies the duration of the benchmark in seconds, in this case, 120 seconds (2 minutes).
• --numjobs=4: Specifies the number of parallel jobs or threads to be used for I/O operations, in this case, 4 jobs.
• --time_based: Tells fio to use a time-based workload rather than a per-request-based workload.
• --group_reporting: Enables grouping of output reports for multiple threads or jobs.
• --name=${job_name}: Specifies a name for the job or workload. ${job_name} is a placeholder that should be replaced with the desired name.
• --eta-newline=1: Outputs estimated time of arrival on a new line.
• --readonly: Specifies that the I/O operations should be read-only, meaning no writes will be performed.

Overall, this command will run the "fio" tool with the provided parameters to perform a read-only benchmark on the specified file or device for a duration of 2 minutes, using 4 parallel jobs and 256 I/O depth.