Partition alignment

[Thomas Hungenberg <th+lists-debian@demonium.de>]

Hi,

I have a 4TB HDD with 4k sectors:

Disk /dev/sdb: 976754642 sectors, 3.6 TiB
Logical sector size: 4096 bytes

I would like to set up a single partition using GPT.

gdisk sets up the partition to start at sector 8 by default:

Number  Start (sector)    End (sector)  Size       Code  Name
   1               8       976754636   3.6 TiB     8300  Linux filesystem

gdisk then is fine with the alignment:

No problems found. 2 free sectors (8.0 KiB) available in 1
segments, the largest of which is 2 (8.0 KiB) in size.

However, parted says the partition is not aligned:

# parted /dev/sdb align-check opt 1
1 not aligned


According to this howto
<http://rainbow.chard.org/2013/01/30/how-to-align-partitions-for-best-performance-using-parted/>

the first partition should start at sector 65535 with my HDD's parameters:

# cat /sys/block/sdb/queue/optimal_io_size
268431360
# cat /sys/block/sdb/queue/physical_block_size
4096

268431360 / 4096 = 65535

So I changed the start sector accordingly:

Number  Start (sector)    End (sector)  Size       Code  Name
   1           65535       976733639   3.6 TiB     8300  Linux filesystem

Now parted is fine with the alignment:

# parted /dev/sdb align-check opt 1
1 aligned

But gdisk complains:

Caution: Partition 1 doesn't begin on a 8-sector boundary. This may
result in degraded performance on some modern (2009 and later) hard disks.


So I wonder which start sector I should choose for optimal alignment?


Thanks,
Thomas