[Bug 244356] Writing to a USB 3.0 stick is very slow

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244356

--- Comment #51 from Olivier Certner <olivier.freebsd at free.fr> ---
(In reply to Hans Petter Selasky from comment #50)

Indeed, I observed the 64KiB limit for USB 2.0. I was talking about USB 3.0
sticks, for which I cannot seem to get bigger transactions than 128KiB.

Both Linux and MacOSX, according to `iostat`, seem to use 1MiB transactions on
these, and seem to get a little bit more bandwidth for sequential access (to a
file, not to the disk directly, so FS clustering comes into play, and probably
several other things). Unfortunately, I did not keep logs for these tests (on
SD_64G and SD_128G, see comment #45), and I don't recall the exact bandwidth
advantage. I'm doing a new round of tests with KT_32G, and at least on MacOSX,
I get comparable performance (a bit lower in fact) despite the different
transaction size. Anyway, the speed differences here are second order to what
prompted the opening of this bug, and possibly not even relevant to
non-sequential access.

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