Hello, I am trying to divide a 4TB hard disk into 128 equal parts. Therefore I divide the disk size (in Bytes) with 128 - this is my increment size. Then I start several fio job rounds with the offset increasing every round by the increment. Unfortunately I get an error for the first offset not equal to 0. I suppose this is an issue with the offsets not being correctly aligned. Here is my call to fio: $ sudo /usr/local/bin/fio --rw=randrw --name=wd --offset=31256148672 --direct=1 --bs=64k --filename=/dev/sdi --rwmixread=100 --numjobs=1 --ioengine=libaio --runtime=60 --iodepth=16 --size=31256148672 --group_reporting --debug=all Here is the error message and the debug output: [...] random 18174 off rand 2400737531 random 18174 free: b=266586, idx=4165, bit=26 random 18174 free: b=266586, idx=4165, bit=26 io 18174 fill_io_u: io_u 0x16ed510: off=48727128768/len=65536/ddir=0//dev/sdi io 18174 prep: io_u 0x16ed510: off=48727128768/len=65536/ddir=0//dev/sdi io 18174 ->prep(0x16ed510)=0 io 18174 queue: io_u 0x16ed510: off=48727128768/len=65536/ddir=0//dev/sdi io 18174 calling ->commit(), depth 16 io 18174 io_u_queued_completed: min=1 io 18174 getevents: 1 io 18174 io complete: io_u 0x16eff80: off=33141291712/len=65536/ddir=0//dev/sdi fio: io_u error on file /dev/sdi: Invalid argument read offset=33141291712, buflen=65536 file 18174 put file /dev/sdi, ref=17 io 18174 io_u_queued_completed: min=0 io 18174 getevents: 1 io 18174 io complete: io_u 0x16efcb0: off=54394616512/len=65536/ddir=0//dev/sdi fio: io_u error on file /dev/sdi: Invalid argument read offset=54394616512, buflen=65536 file 18174 put file /dev/sdi, ref=16 fio: pid=18174, err=22/file:io_u.c:1305, func=io_u error, error=Invalid argument file 18174 close files file 18174 put file /dev/sdi, ref=15 I am happy with any suggestions =) Best regards Georg -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html