>>>>> "Chris" == Chris Murphy <lists@xxxxxxxxxxxxxxxxx> writes:
Chris> Huh. Two more cases. All three involve USB enclosures. Bug or
Chris> feature?
Feature.
Chris> Is it possible the enclosure's bridge chipset is disabling the
Chris> drive's 512-byte emulation?
There's nothing to disable. If the USB-SATA bridge exposes 4K logical
blocks to the host all accesses will inevitably be aligned multiples of
4K. All the bridge needs to do is adjust LBA and transfer length. Not
unlike how we handle 1/2/4Kn in the Linux SCSI disk driver given that
the block layer always uses 512-byte sectors.
The two 4Kn USB drives I have both use 512e drives internally:
# sg_readcap -l /dev/sdd | grep Logical
Logical block length=4096 bytes
Logical blocks per physical block exponent=0
# hdparm -I /dev/sdd | grep Sector
Logical Sector size: 512 bytes
Physical Sector size: 4096 bytes
Logical Sector-0 offset: 0 bytes
It is conceivable that there are other USB drives out there that
actually use 4Kn drives inside but I doubt it. All the 4Kn SATA drives I
have in the lab are engineering samples...
--
Martin K. Petersen Oracle Linux Engineering
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