[ubuntu-za] File transfer speed

[Xandor Schiefer]

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More than likely, Ubuntu is showing you a transfer speed that counts
"moving files into the disk cache *to be written when there's a nice gap
for disk i/o*" in to the calculation of overall speed.

It's likely not the speed that things are actually being written to
disk. So that disk i/o doesn't unduly interrupt other computing tasks,
the kernel usually fills up a disk cache and waits for an opportune
moment to actually write what's in the cache to disk.

This is why there's an "eject/safely remove/unmount" step we *should*
take before removing removable media that has been written to recently.
It's why if you eject very quickly after a transfer "finishes", you'll
have to wait a bit, but if you did a transfer 10 minutes ago, ejecting
will be nearly instant. There's the CLI command `sync` that will flush
the disk cache to disk.

It's also why, if you're doing a particularly large transfer, the speed
seems really fast at first, and then slows down to a more stable rate.
At first it's filling up the disk cache, and when that's full you're
seeing a more realistic transfer rate.

If you knew about all of that already, and you're confident that's not
it, it could also be that your windows drivers aren't updated/the right
kind for the connection/hardware and it is in a legacy or fallback mode.

Kind regards,


Xandor Schiefer
+27 79 706 5620

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On 08/09/2016 06:15, Jan Greeff wrote:
> Good morning all,
> 
> An interesting question to which I hope to receive even more interesting
> replies.
> 
> When I transfer files and folders to my external hard drive from my
> Ubuntu system, the transfer rate runs at between 26 to 28 MBps.
> When I transfer from the Windoze 7 installation on the same machine to
> the same drive, the transfer rate is less than 1 MBps.
> 
> Why the massive difference in transfer rates?
> 
> Best wishes,
> 
> Jan
> 
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