[TriLUG] 512/4096B cluster size incompatibilities

[Joseph Mack NA3T via TriLUG]

On Sat, 29 Dec 2018, David Burton wrote:

> I believe that all 4 TB drives use 4K hardware sectors.

> So I doubt there's a hardware or firmware difference between your two
> drives. It must be a partitioning / formatting issue. What does  * fdisk
> -lu*    show?
>
> Or maybe it's a hardware issue. What does   smartctl -a /dev/sd*x*   show
> for each drive?

Hi David,

Thanks for getting back to me.

Here's /dev/sdb

--

#smartctl -a /dev/sdb | more

smartctl 6.6 2017-11-05 r4594 [i686-linux-2.6.37.6-smp] (local build)
Copyright (C) 2002-17, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Seagate Desktop HDD.15
Device Model:     ST4000DM000-1F2168
Serial Number:    S300Z0B3
LU WWN Device Id: 5 000c50 07584241b
Firmware Version: CC54
User Capacity:    4,000,787,030,016 bytes [4.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical

# fdisk -lu /dev/sdb

Disk /dev/sdb: 3.7 TiB, 4000787030016 bytes, 976754646 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 87410DEA-1C98-40C8-8B6A-07C07368D588

Device        Start       End   Sectors  Size Type
/dev/sdb1      2048   2623487   2621440   10G Microsoft basic data
/dev/sdb2   2623488   5244927   2621440   10G Linux swap
/dev/sdb3   5244928  15730687  10485760   40G Microsoft basic data
/dev/sdb4  15730688 976754640 961023953  3.6T Microsoft basic data

--

Here's /dev/sdc

#smartctl -a /dev/sdc | more

smartctl 6.6 2017-11-05 r4594 [i686-linux-2.6.37.6-smp] (local build)
Copyright (C) 2002-17, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Seagate Desktop HDD.15
Device Model:     ST4000DM000-1F2168
Serial Number:    Z301AWEC
LU WWN Device Id: 5 000c50 065f798fe
Firmware Version: CC54
User Capacity:    4,000,787,030,016 bytes [4.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical

# fdisk -lu /dev/sdc

Disk /dev/sdc: 3.7 TiB, 4000787029504 bytes, 7814037167 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
Disklabel type: gpt
Disk identifier: D5AFB6EC-6F9E-43DF-A6F9-89D8E9A82305

Device         Start        End    Sectors  Size Type
/dev/sdc1       2048   20973567   20971520   10G Microsoft basic data
/dev/sdc2   20973568   41945087   20971520   10G Microsoft basic data
/dev/sdc3   41945088  125831167   83886080   40G Microsoft basic data
/dev/sdc4  125831168 7814037133 7688205966  3.6T Microsoft basic data

--

Both disks are ST4000DM000-1F2168 with firmware version CC54

Both disks were partitioned with the same gdisk

# gdisk --version
GPT fdisk (gdisk) version 0.6.14

I partitioned the disks by setting the partition sizes, not the number of 
sectors. The number of sectors is different in the two disks (same partition 
size).

from the output of fdisk the sector sizes are different.

/dev/sdb

Sector size (logical/physical): 4096 bytes / 4096 bytes

/dev/sdc

Sector size (logical/physical): 512 bytes / 512 bytes

In one of my external drive cases, the 512B drive works fine, but the 4096B 
drive is not recognised (nothing in /dev/sd*, and a flashing LED).

> But, also, if a 4 TB drive had 512-byte physical sectors then the sectors 
> couldn't even be addressed, internally, within the drive, without using more 
> than 32 bits for the sector numbers.

I assumed that large drives were all addressed with more than 32bits, although I 
didn't know how. I would have thought it easy enough to increase the logical 
sector size and stay with 32bit addressing as the drives got larger.

> Modern drives support LBA48,

had not heard of it. I just looked it up in wikipedia. It's been a long time 
since I worried about disk sectors. Thanks for the pointer.

If indeed the disks have different sector sizes (and I'm not doing something 
silly), I'm a bit peeved that Seagate would do this.

Thanks
Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant
map generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!