USB-3 file transfer speed indications

Issues related to hardware problems
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Posts: 43
Joined: 2018/02/17 19:09:47

USB-3 file transfer speed indications

Post by john2018 » 2018/06/20 15:26:28

I'm running Centos 7 on an intel i7-8700 system with 32GB ram.
The drive is a GPT 4TB WD Elements with 2 partitions both formatted NTFS
I'm using NTFS-3g.
The copy is from partition 1 to partition 2.
I am using a USB 3 port with the supplied drive cable connected.

While trying to copy a folder containing files of between 1 and 2GB each up to a total of 140GB
I'm seeing wild fluctuation in reported transfer speed making estimated copy time impossible.
The variations go from 600KB/S to about 112MB/s Fluctuation is continual not from file to file.

Additionally stopping the copy and using the safe drive removal option reports it is safe
to remove the drive even though the drive is still active for more than 5 minutes more.

So the questions are:
Have I missed a config setting
is this normal
Has anyone else had anything similar etc?


Posts: 530
Joined: 2017/02/22 15:08:17

Re: USB-3 file transfer speed indications

Post by tunk » 2018/06/20 16:02:17

I would guess it depends on how fragmented your files are and how full partition 2 is.
Also both source and destination is on the same disk which will slow it down.
Is it the same if you do the copy on a windows PC?

Posts: 43
Joined: 2018/02/17 19:09:47

Re: USB-3 file transfer speed indications

Post by john2018 » 2018/06/21 07:12:00

Neither partition is fragmented hardly at all.
(I did think of that initially)
I deleted the folder and tried on win7-64 and it copied smoothly
at about 28MB/s (That one is an old PC with USB3 card)
There is some minor movement but when it settles down it's fairly stable.

On Centos the speed is constantly bouncing all over the place
sometimes showing as little as 13 minutes and other times
showing 17 days to complete. It doesn't stay still for more
than a second.
(It might just be a reporting averaging issue - I just don't know)

I'll try copying some large files on a non GPT formatted drive
and other variations to see if it varies.
(This is a new machine I built recently but only now have acquired
enough data to do this sort of thing so I don't know if I have something
miss-configured - or what if anything that could be)

The safe to disconnect issue I think I mentioned elsewhere in passing
but that now is disturbing as it does seem regular.
(The drive activity light is flashing long after centos says its safe to unplug it)

Posts: 496
Joined: 2013/12/08 19:44:49

Re: USB-3 file transfer speed indications

Post by chemal » 2018/06/22 00:35:01

Issue as root

Code: Select all

echo $((16*1024*1024)) > /proc/sys/vm/dirty_background_bytes
echo $((48*1024*1024)) > /proc/sys/vm/dirty_bytes
and then try again. If it helps, you can add these two lines to /etc/rc.local. (Linux' habit of buffering writes is not really helpful with external drives.)

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