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I use Ubuntu 12.04.

I have a good PC , a Dell XPS, with 8 GB of memory and a 1TB HDD and an i5 processor.

When I copy files internally (to and from the internal HDD), nautilus initially shows speeds of about 30 Mb/s. But, the problem is, it always, keeps dropping by 0.1 Mb/s at a time (every 5 seconds or so), till it stabilizes at around 1Mb/s (if the copying isn't finished already).

I'm trying to backup my PC into a 1TB WD My Passport external HDD (USB 3.0). It started at 36 Mb/s and is now 8Mb/s in 15 minutes and still falling regularly. I have around a 100 GB of data to copy and it doesn't seem it will happen.

Any ideas about the problem?

EDIT: While I couldn't really find out what caused th problem, using a tool like rsync helped and it is much faster than the traditional cp.

Sebastian Werk's answer helped too, but it doesn't tell what caused it.

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Check out packages.ubuntu.com/precise/iozone3 which is a benchmarking tool. Will need to install as its not standard. At least it will be a bottom level test to see if its a low level problem –  Meer Borg Mar 15 '13 at 9:45
    
What test should I do using izone3? –  learner Mar 15 '13 at 10:06
    
Use this as a guide thegeekstuff.com/2011/05/iozone-examples –  Meer Borg Mar 15 '13 at 10:22
    
My output from a crapy USB2 external drive paste.ubuntu.com/5616102 command used included in output, note to execute command,change directory to the drive in question –  Meer Borg Mar 15 '13 at 10:27
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1 Answer

Have not the required reputation for comments, that’s why I post this as an answer:

I assume the external HDD is not a SSD, but a „normal“ HDD.

  • Was it empty?
  • How much data do you copy? 1 entire TB?
  • Which file system do you use? (FAT, NTFS, ext, ...)
  • Do you copy a lot of small files or a handful of big files?

If the harddisk was not empty and FAT as a filesystem was used, there might be the problem, that big files have to get split up amoung different locations, this usually slows down.

Some filesystems (ext for instance) distribute the files all over the disk (which is good!), but if you copied first a lot of small files, then you might run in the same problem when big files arrive.

When a disk is almost full, the performance usually drops a lot.

And finally, the nautilus speed display is not very precise in general.

Probably it is too late now, but you can test the performance of a disk via the „Disks“-program, if this drop to 1 MB/s is a general problem.

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Since I mostly copy inside my internal HDD, it is generally half full. My external was empty. I use NTFS file system. I usually see this issue when I copy above 5 GB. This time, I copied 30 GB. I normally copy audio/video/code files. –  learner Mar 15 '13 at 10:03
    
Half full seems to be empty enough. You could try to use pv for copying one very big file, this gives you the „real“ speed and not some averages as nautilus. –  Sebastian Werk Mar 15 '13 at 10:21
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