[maemo-users] Slow writes from linux to N900 in USB Mass Storage Mode

From: Paul Hartman paul.hartman+maemo at gmail.com
Date: Sun Dec 27 23:38:03 EET 2009

I'm using linux kernel 2.6.32 on my PC and mount N900 in mass storage
mode using vfat (async).

If I write one file then sync/umount, write speed is about 17MB/sec,
same as I get on Windows Vista. However, if I write more than one file
and then sync/umount, speed is terrible, around 2MB/sec (and in kernel
2.6.31 that speed was about 450kb/sec using the old pdflush code). So
it seems linux is maybe creating multiple write streams and N900
doesn't deal with that well at all.

Size doesn't seem to matter, copying one 1gb file followed by sync is
around 8 times faster than copying 2 500gb files followed by sync. In
other words, as long as every single file copy is followed immediately
by sync before moving on to the next file, speed is fine. If more than
1 file is copied before sync, it's bad.

Does anyone else experience the same problem or have any ideas how to
solve it? I'm no USB guru an every other USB device I have seems to
work properly and at full speed. dmesg shows no messages (on PC) and
it is running USB 2.0 etc.

So far my only workaround is to copy/sync/copy/sync/copy/sync but
that's annoying. However, the difference of taking 1 minute to write
1gb versus taking 20 minutes to write 1gb is also annoying.

Thanks :)
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