Re: Slow rsync speed between usb drives

It looks like in general write speeds on the NSLU2 are being slow:

docbillLKG6BE74A:~$ dd if=/dev/zero of=/tmp/x bs=4096 count=100000
100000+0 records in
100000+0 records out
409600000 bytes (410 MB) copied, 197.421 seconds, 2.1 MB/s

According to
http://www.nslu2-linux.org/wiki/Unslung/SolvePerformanceProblems

I should be seeing about 10 MB/s. Although, I notice the dd on that
page only copies 10M, which is not enough for a proper though put
test. Particularly if none of the data synced to disk during the write.

Reading a disk is not much faster:

docbillLKG6BE74A:/proc/sys$ dd if=/tmp/x of=/dev/null bs=4096
100000+0 records in
100000+0 records out
409600000 bytes (410 MB) copied, 115.896 seconds, 3.5 MB/s

I don't see any useful log entries with dmesg.

--- In nslu2-general%40yahoogroups.com">nslu2-generalyahoogroups.com, "Carl Lowenstein"
<clowenstein...> wrote:
>
> On 3/26/08, docbillnet <yahoo...> wrote:
&gt; >
>; > Hello,
&gt; >
>; > I just purchased a couple of NSLU2 from tigerdirect.ca, and I have
>; > followed the instructions for installing Linux on one. Overall, it
> > seems to be working well, especially since I cut the resistor.
> > However, I wanted to backup data from three 500 GB drives to a 1.5 TB
> > drive. However, when I used the --progress option with rsync, it
> > reported the transfer speed is 2.0 MB/s. After a quick back of the
> > envelope calculation, I concluded it will take 8 days to copy my data
>; > from the three drives.
>
> Exactly what command did you give rsync?
&gt;
> Did you possibly enable either encryption or compression? Neither of
> these are necessary for a local transfer, and both of them are
> computationally intensive. The NSLU2 has a CPU of very little brain.
&gt;
>
> > So, I shutdown the NSLU2, and plugged the same drives and USB hub
into
> > my laptop. I issued the same rsync command, and my transfer rate is
> > 20 MB/s.
&gt;
> You couild do the initial backup with the laptop, taking one day
> according to your calculations. Updating the backup with the NSLU2
&gt; and rsync will take much less time, because only the changes are
> transferred.
>
> carl
>; --
> carl lowenstein
> marine physical lab, u.c. san diego
&gt; clowenstein...
>;

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