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Date:      Mon, 23 Jul 2012 09:40:20 +0200 (CEST)
From:      Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To:        Jakub Lach <jakub_lach@mailplus.pl>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: "da0: 40.000MB/s transfers" What was rationale behind pegging USB 2.0 at 40MB/s?
Message-ID:  <alpine.BSF.2.00.1207230937150.7616@wojtek.tensor.gdynia.pl>
In-Reply-To: <1342994216549-5729035.post@n5.nabble.com>
References:  <1342992043358-5729028.post@n5.nabble.com> <alpine.BSF.2.00.1207222331130.4614@wojtek.tensor.gdynia.pl> <1342994216549-5729035.post@n5.nabble.com>

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> dd if=/dev/zero of=/dev/da0 bs=1 to 15M
>
> runs, 13-14MB/s from actual files copied
> in mc to flash and 36-39MB/s file copied
> from flash to hdd in mc.
>
> dd if=/dev/da0 of=/dev/zero bs=15m
>
> gives 33MB/s read.
and this is incredibly high as of any pendrive.

Consider few things:

- pendrive flash mappers are incredibly dumb, they work in usable speed 
when you do linear write only.

- today lies are standard. never believe in stated performance unless you 
measure it.


> even recognized in FreeBSD as device.
what i do with any pendrive:

dd if=/dev/zero of=/dev/da0 bs=64k count=1
newfs_msdosfs /dev/da0 (if i want FAT filesystem)

partition table is not needed in any OS, including Windows starting from 
XP.


msdosfs in FreeBSD isn't high performance too.

try writing small amount of huge files.



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