On 9 February 2018 at 04:21, Gnana Sekhar <kgsgnana2020@xxxxxxxxx> wrote: > > Below is the drive information > blockdev --getsize64 /dev/nvme0n1 > > 3840755982336 > > fdisk -l > > Disk /dev/nvme0n1: 3840.8 GB, 3840755982336 bytes, 7501476528 sectors > Units = sectors of 1 * 512 = 512 bytes > Sector size (logical/physical): 512 bytes / 512 bytes > I/O size (minimum/optimal): 512 bytes / 512 bytes > > I had to change the sector size from 4K to 512 and now I didn't see > the failure mentioned below. Will loop through and update Seems strange that the problem would go away just due to shrinking fio's blocksize given that 4k is a multiple of 512. You never said if dmesg showed any clues though... > I was using offset and sizeToWrite parameters when I wanted to fill > certain number of bytes from certain start location. > Currently I am using "sizeToWrite" to specify the bytes to write and > "offset" from the byte to start > But from the suggestions it seems I have to chose the offset such that > its divisible by blocksize of filesystem. I am using blockdev --getbsz Note in the examples you gave you were not doing I/O to a file in a filesystem - you were just writing directly to a disk so I'm going to assume you just mean disk where you have written filesystem :-) But yes, you will have to ensure an absolute offset is a multiple of the disk's block size when doing direct IO to a disk on Linux. > Let me know if you guys think that should solve the problem or you > come across any other optimal way to do the same without using offset > and sizeToWrite Only passing in an aligned offset should solve the problem and I'm not aware of anther way. > Also which of the below do you think I should use to get the LBA size on device > blockdev --getbsz /dev/nvme0n1 or blockdev --getss /dev/nvme0n1 Either will do but if I were choosing I'd prefer the number from getbsz. From what I can see getbsz corresponds to the physical block size (which is closer to the minimum block size the "disk" actually has to use behind the scenes) and getss corresponds to the logical block size (the minimum block size your "disk" can accept even if it means it means faking it and doing extra work). -- Sitsofe | http://sucs.org/~sits/ -- 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
