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Date: Sun, 1 Jul 2018 12:17:41 -0700
From: bob prohaska <fbsd@www.zefox.net>
To: Mark Millard <marklmi@yahoo.com>
Cc: Trev <freebsd-arm@sentry.org>, freebsd-arm@freebsd.org,
 bob prohaska <fbsd@www.zefox.net>
Subject: Re: RPI3 swap experiments
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On Sat, Jun 30, 2018 at 11:42:00PM -0700, Mark Millard wrote:
> 
> 
> So I tend to use a powered hub for USB storage.
> 

It occurs to me that a powered hub provides more than power: It provides delay.
Likely not much, but a flash device has none of the rotational or seek delay
of a mechanical drive. At least occasionally, a flash device might respond
quicker than any plausible mechanical one. If the host isn't ready, it'd miss
the response. Most "disk" driver software was written in the days of mechanical
disks, is it possible assumptions about minimum response delay were made?
There's doubtless a "re-training" scheme to get host and device back in sync,
but if the timings remain wrong that would prolong the confusion.
 
Thanks for reading,

bob prohaska