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I am using ubuntu 18.04 with KDE Plasma after i upgraded from 16.04. I did some research and so far i understand that before the actual file transfer, files are cached in the ram so they can be fetched faster to the removable media.

So i was trying to copy 2GB of DSLR photos from my laptop m2.ssd to my ntfs usb stick probably usb 2.0. It takes around 15 minutes.

Dolphin and probably other file managers or programs misinform the user when it comes to progress. When i begin copying the files, the progress shown is pretty fast and ends within seconds(may vary). This happens even with cp and rsync.

So i guess the progress shown is actually the caching to the RAM. The reason i believe that is because:

a) Even after those program say the job is done, my usb light keeps blinking.

b) When i try to unmount the usb, it hangs(maybe phrased wrongly, it waits probably until the copying is finished) even though dolphin has informed me that the job is complete.

If i pull out the usb, it corrupts the data and i end up formatting it with disks because the permissions to the files are all messed up.

Questions:

1) Why does ubuntu handle usb like that? Shouldn't it keep track of the progress like windows?

2) Is there a way to get a windows-like file transfer progress? I can't be using iostat or whatever every time i want to copy files from/to usb.

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    Linux (Ubuntu) verifies the file after or before transfer so that delay might mean that the verification is still going on! – George Udosen Sep 15 '18 at 22:37
  • Can you elaborate on that maybe? What do you mean with verification? Do you have a source? – sstam Sep 15 '18 at 23:07
  • Sounds like bug bugs.launchpad.net/ubuntu/+source/nautilus/+bug/799601 Click on the yellow button after the question ... Does this bug affect you? to add yourself to the bug. If the umount is just waiting for the copy to finish, I wouldn't call that a "hang". – ubfan1 Sep 15 '18 at 23:09
  • I rephrased "hangs". My issue is not specifically with nautilus. If the usb needs to go, the user has to manually find and stop the copying process (which is in the background) in order to be able to unmount and not corrupt his data. I find that so wrong for a desktop OS even though i like fiddling with the terminal. – sstam Sep 15 '18 at 23:26
  • By "When i try to unmount the usb, ..." do you mean the Safely remove feature of Dolphin? – DK Bose Sep 15 '18 at 23:51
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You have described the process accurately, with applications considering their part of the copy job done as soon as they pass the last byte to the system (buffers). umount and/or sync will wait until the system buffers flush before finishing. iostat is actually a good way to track the system activity on a device, but the blinken light on the USB is your friend. The "safe unmount" offered by the file GUI should also popup some notification when the buffers are flushed. Big file copies can be very much slower than you have reported, so you haven't even seen the worst until you try to copy a 50G virtual machine. Take a look at the "slow copy" bugs, and your results seem right in line with what others see.

As to why, well, UNIX was always a multitasking OS, so having a program finish and free up its memory was seen as good. Tying up that program memory waiting for slow I/O was bad.

On my big copies, I find using a copy program like tar or cpio where I can specify a buffer size helps (e.g. give tar several megs of buffer, that seems to unload the system memory allocator somewhat, or keep memory fragmentation down or something.

  • Ok, so this is the expected behaviour. Again i believe they should add better progress handling features. e.g When copying starts, a small windows shows the overall progress and in the dropdown details section it tracks both the buffering and the actual progress. – sstam Sep 16 '18 at 12:36
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This problem is specific to Dolphin. I tried differents desktop and most of them are performing very well with USB stick. After loosing 3 months of work , i had switch for Cinnamon. Plasma is a very good desktop. But Dolphin is crap.

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