From owner-freebsd-hackers@freebsd.org  Sat Jul 11 23:14:51 2015
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Date: Sat, 11 Jul 2015 17:14:49 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Dieter BSD <dieterbsd@gmail.com>
cc: freebsd-hackers@freebsd.org
Subject: Re: format/newfs larger external consumer drives
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On Sat, 11 Jul 2015, Dieter BSD wrote:

> USB specific stuff: There is an off by 1 sector problem, which will
> bite you if you switch a drive between using the sata-usb bridge
> and connecting the drive directly to a sata controller.  I had to
> do a fair bit of hacking on the kernel to deal with this.  (No,
> I don't have a nice clean patch to offer, sorry.  Besides, I just
> plastered over the problem rather than hunting down and fixing the
> root cause, which is what really needs to be done.)  I don't recall
> if it is off by one physical sector, or one logical sector.  On a
> 4 KiB drive it *might* mess up having things be on 4K multiples.
> Word is that the disk manufacturers have changed the interface
> between the bridge and the drive on recent external drives, making it
> difficult-to-impossible to use the drive connected directly to a sata
> controller. :-(

This depends on the USB-SATA adapter.  Some have bugs.  Some give one 
less block that the drive's capacity by accident, some keep metadata in 
the last block.  I've seen it, but only rarely with the USB-SATA 
adapters I've had.