The way linux assign names to disk drive is as follows:
HD/x/n:
HD- denotes that the disk drive is IDE based, if the drive is SCSI or SATA based, it will be designated as SD.
x-denotes the position of the drive. If it's installed in the IDE controllers as the primary master it will be designated as HDA. If as the primary slave it will be designated as HDB. If as the secondary master, HDC. HDD if the drive is installed as the secondary slave.
n- this denotes the partition number. For example, the first partition of the Primary Master will be designated as HDA1. Usually the primary partitions are designated with the number 1-4. The logical drives are given the number 5-n depends on how many logical partitions you have.
HD/x/n:
HD- denotes that the disk drive is IDE based, if the drive is SCSI or SATA based, it will be designated as SD.
x-denotes the position of the drive. If it's installed in the IDE controllers as the primary master it will be designated as HDA. If as the primary slave it will be designated as HDB. If as the secondary master, HDC. HDD if the drive is installed as the secondary slave.
n- this denotes the partition number. For example, the first partition of the Primary Master will be designated as HDA1. Usually the primary partitions are designated with the number 1-4. The logical drives are given the number 5-n depends on how many logical partitions you have.