hdd partition alignment parted vs fdisk, partition 1 does not start on physical sector boundary, parted bug?

[Sergey Spiridonov <sena@s73.work>]

Hi all

I am trying to partition 14TB HDD and get the following problem with an 
alignment:

# hdparam -I /dev/sdd tells that 

	Logical  Sector size:                   512 bytes
	Physical Sector size:                  4096 bytes


# parted -a opt /dev/sdd

(parted) mkpart primary 0% 100%
...

(parted) print 

Number  Start   End     Size    File system  Name     Flags
 1      33,6MB  14,0TB  14,0TB               primary

Now checking alignment:

(parted) align-check opt
1 1 aligned


So far, so good. Now let's look at the same disk with fdisk:

# fdisk /dev/sdd

: p

Disk /dev/sdd: 12,8 TiB, 14000519643136 bytes, 27344764928 sectors
Disk model: IB-366StU3+B
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 33553920 bytes
Disklabel type: gpt
Disk identifier: 82DD924B-BF0E-40FF-9037-1FD4E7307D26

Device     Start         End     Sectors  Size Type
/dev/sdd1  65535 27344740889 27344675355 12,8T Linux filesystem

Partition 1 does not start on physical sector boundary.


What? Why?


man parted tells that

   optimal
                  Use optimum alignment as given by the disk
                  topology  in‐ formation.  This  aligns  to  a
                  multiple of the physical block size in a way that
                  guarantees optimal performance


1. Probably parted detected physical sector size as 512
instead of 4096? Why?

2. Even if parted thinks that physical sector is 512 instead of
4096, why start from 65535 and not from 65536? What is the logic
behind? How using odd multiplier can improve performance?

Is it a bug in parted or I am missing something?
-- 
Best regards, Sergey Spiridonov