I am running a DD benchmark but the obtained results are not matching with the IOSTAT values.

This is the DD sample:

$ sudo dd bs=4096 count=690 if=/dev/zero of=/mnt/tmp/test oflag=dsync
690+0 records in
690+0 records out
2826240 bytes (2,8 MB) copied, 29,2135 s, 96,7 kB/s

While this benchmark is running, the "iostat -x 1" is reporting on "wkB/s" values between 500 and 600 kB/s.

Something's wrong here.. well, if I don't use the DSYNC, the values are matching.. but I want to do a constant sync for each write operation. Maybe IOSTAT doesn't work well with DSYNC operations ?!

Does anyone know what's the problem here?


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