On Jun 22, 2014, at 1:49 AM, Imran Geriskovan <imran.gerisko...@gmail.com> wrote:
>> The 64KB Btrfs bootloader pad is 8 sector aligned, so for 512e AF disks >> there's no problem formatting the whole drive. The alignment problem >> actually happens when partitioning it, using old partition tools that don't >> align on 8 sector boundaries. There are some such tools still floating >> around. > > A 'somewhat' related question: > > So called Advanced Format drives has 4K physical sector size, > however they report 512B logical sector size. > > How does linux kernel access those drives? > 512B or 4K at a time? Does anyone know if blktrace will intercept the actual SCSI commands sent to the drive? Or is there a better utility to use for this? When I use it unfiltered, I'm not seeing SCSI write commands at all. This is the blktrace/blkparse for dd if=/dev/zero of=/dev/sda seek=430234064 count=8 oflag=direct https://docs.google.com/file/d/0B_2Asp8DGjJ9c3J0UXpzUEhNaGs/edit?pli=1 This is the blktrace/blkparse for dd if=/dev/zero of=/dev/sda bs=4096 seek=53779258 count=1 https://docs.google.com/file/d/0B_2Asp8DGjJ9MnEwU0hDNE45dHc/edit?pli=1 The dd command clearly shows a difference, but when I look at the ATA command set I'd expect the Linux SCSI layer to turn these dd commands into the same ATA command: basically a write start LBA and sector count. And the LBA and sector count can only be in 512 byte sector addresses because that's all a 512e type of AF disk understands. Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
