[Bug 247964] Low read throughput on Sandisk Extreme external SSD

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 20 Sep 2021 08:14:59 UTC

Gary Jennejohn <gljennjohn@gmail.com> changed:

           What    |Removed                     |Added
                 CC|                            |gljennjohn@gmail.com

--- Comment #2 from Gary Jennejohn <gljennjohn@gmail.com> ---
(In reply to Tom Jones from comment #0)
You don't state which USB version you're using, but based on the transfer
speeds it must be USB3.
Not all USB3 ports/external enclosures are created equal.  Is it USB3.0, USB3.1
or USB3.2?  You don't state which USB3 versions your various computers support.
For example, my FreeBSD box supports USB3.1 Gen 1 and, using the dd values you
provide, I get a transfer rate of 378MB/s from a 1TB Samsung SSD 870 EVO (when
I plug it in the USB stack reports 400MB/s transfers).  When I plug this SSD
into a Linux server, which only has USB3.0 support, I get only a 205MB/s
transfer rate, while using the equivalent Linux dd command.
So, don't blame FreeBSD alone.  The USB3 hardware plays a big role in transfer
Note that the Linux server has a AMD 6-core 3.2GHz CPU and the FreeBSD box has
a Ryzen 7 3700X.  But the CPU shouldn't a bottleneck for USB transfers.

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