I traced the traffic to a usb stick via wireshark.
I tried using different ways to write and read to and from the device.
Whenever i used dd to write directly to the device i saw a number of additional read commands a few moments after my write command was completed.
When i formatted the device with fat32, mounted it and copied files over, i did not see these read commands.
They are mostly to the first few sectors and what look like the last sectors of the device.

Can anyone tell me what these reads are? And maybe where in the kernel code i can find the code responsible for them?
Or any idea what could have caused them would be appreciated.

Bonsi

Welcome to LinuxQuestions.

Writing to disk is not synchronous by default. Since writing to disk is much slower the data is buffered and the write operations are performed in the background. Although you will see the next command prompt in a few moments it does not always indicate the previous command actually completed in the case of disk writes.

It depends on how much data you are writing. Formatting FAT32 does not write much data to disk i.e. two FAT tables, one at the beginning and a spare at the end as you have posted.

Thank you.

The read commands sent to the device seem to come as a reaction to the write command that i sent.
The writing via FAT32 filesystem is after the formating. I copy a couple MB to the mounted device.