Must write data before running a read benchmark!

This error message typically occurs when you are trying to run a read benchmark on a storage device that has not yet been written to. In order to perform a read benchmark, there must be data present on the device to read from.

To resolve this error, you can try writing some data to the storage device before running the read benchmark. This can be done by copying some files onto the device, creating a new file on the device, or using a disk benchmarking tool that includes a write test.

Once you have written some data to the device, you should be able to run the read benchmark without encountering the "Must write data before running a read benchmark!" error.