writing data to disk message... when safely remove USB drive

[Basil Chupin]

On 06/05/13 14:46, Amichai Rotman wrote:
>
>
> On Sun, May 5, 2013 at 3:17 PM, Basil Chupin <blchupin at iinet.net.au 
> <mailto:blchupin at iinet.net.au>> wrote:
>
>     On 05/05/13 20:10, Jkhatri wrote:
>
>         On Sunday 05 May 2013 <tel:2013> 03:31 PM, Colin Law wrote:
>
>             On 5 May 2013 <tel:2013> 10:54,
>             Jkhatri<khatri.jatin at gmail.com
>             <mailto:khatri.jatin at gmail.com>>  wrote:
>
>                 Dear ALL
>
>                 I'm facing one strange issue, whenever I copy some
>                 data to USB thumb drive (
>                 some big files, say 2GB .avi or something) its
>                 displays progress bar on
>                 screen that data is being copied to disk and finally
>                 it finished but strange
>
>
>                 why like that ???
>
>                 several minutes after the copy before attempting to
>                 eject you should
>                 find it then ejects immediately (as the write is
>                 complete).  If it
>                 becomes very slow on a particular stick that probably
>                 means that it is
>                 failing as it takes longer to write as the flash wears
>                 out.
>
>                 Colin
>
>         Thanks for your quick reply, colin
>
>         but same drive works fine with M$ windows, on same PC ( dual
>         boot ). it copies same file quickly, and I'm able to eject it
>         as soon as copy process completed. But it takes long time in
>         Ubuntu it takes dual time, like  copy time + safely remove
>         message progress bar time
>
>         both windows and Ubuntu are 64bit version and installed on
>         same laptop ( dual boot )
>
>         Thanks
>
>
>     You get fast copying in M$ because the stick is formatted in msdos.
>
>     Writing from Linux to a msdos formatted drive, such as your USB
>     stick, takes "for ever". There is a very complicated explanation
>     for this but believe me it is true (something to do with the kernel).
>
>     Format the USB stick in a linux format, say ext4, and you will
>     find that the copying will be fast (and even faster if the USB is
>     usb3 and connected to your usb3 port on your computer; usb2 you
>     will get around 28MB/s but with usb3 you should get around 110MB/s
>     [but depending on the brand of stick you have]).
>
>     BC
>

PLEASE don't top-post. Thank you.

And because you top posted I have transferred what you wrote here so 
that I can respond to your post:

QUOTE

That's the way Linux saves data to disk. When you transfer a large file 
to an external device (not part of the local file system), it keeps the 
data in a memory cache. The kernel finds the best time to periodically 
flush that cache to disk.
You have two options to run after the progress bar disappears:
1. Click Safely Remove and wait until you get the "It is now safe to 
remove the..."
2. Drop to a Terminal window and run 'sudo sync' - and wait until the 
prompt comes back (that is what I do when I transfer large sized files).
3. Unplug the USB device (be it a USB stick or external hard drive.
Your files are actually written to the external drive at that point. if 
you skip that stage (2), the copy operation is cancelled.
Amichai.


UNQUOTE

My response did not address the *method* of copying but the fact that if 
you copy from linux to a msdos formatted partition the speed of copying 
is slow. (The bottom line for this is the fact that the ability in linux 
to copy to msdos is a kludge.)

I think that we all know that when a copy is being made to an USB disc, 
or even an HDD, the file being copied is buffered and only copied when 
the buffer is (almost) full (you can actually see this if you use k3b to 
burn a disc).

Furthermore, when it comes to memory sticks all of them are notoriously 
slow to *write* data to but always faster to *read* from. If you are 
buying a memory stick look at its specifications and look for its 
read/write speed. (There are a couple of brands which perform quite well 
in respect of this.)

BC

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