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Subject: Re: problems copying over many files

Re: problems copying over many files

From: Johan Vromans <>
Date: Sat, 29 Mar 2003 16:43:01 +0100

"Gerald Clark" <> writes:

> Are you running Linux and USB1 ?
> I suspect it starts out fast as it fills
> Many megs of buffers. When it runs out of buffers, it starts writing them.
> This is the long pause.

The following experiment confirms this.
Note these are figures for USB 2.0. Also note, that this is Linux
kernel 2.4.20.

 # mount /dev/sdd1 /mnt/tmp

Copy a directory with 120Mb (19 files):

 # time cp *.mp3 /mnt/tmp/tmp/
 0.020u 1.790s 0:28.33 6.3% 0+0k 0+0io 138pf+0w

Quickly, do it again:

 # time cp *.mp3 /mnt/tmp/tmp/
 0.010u 1.130s 0:03.21 35.5% 0+0k 0+0io 138pf+0w

Apparently, most of the data is still in the buffer.
Therefore, the umount needs time to flush:

 # time umount /dev/sdd1
 0.000u 0.410s 0:22.20 1.8% 0+0k 0+0io 145pf+0w

These are the figures for USB 1:

 # mount /dev/sdd1 /mnt/tmp
 # cp *.mp3 /mnt/tmp/tmp/
 0.030u 1.130s 3:00.24 0.6% 0+0k 0+0io 130pf+0w
 # time umount /dev/sdd1
 0.010u 0.340s 2:29.06 0.2% 0+0k 0+0io 145pf+0w

-- Johan
Received on 2003-03-29

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