Arch Linux

MajinJoko

Member

Registered: 2007-08-15

Posts: 84

Slow USB write issue

Dear all,
I *think* to have a problem

Lately it seems that writing files on usb flash key takes a long time.
My laptop has a USB 3.0 port and two 2 USB 2.0 ports.

I run some tests yesterday, copying 2 files for a total of 4,1 GB.
1) usb 3.0 flash key connected to usb 3.0 port
-> 2 m 50 s to copy the file
-> a reasonable amount of time to sync
2) usb 2.0 flash key connected to usb 3.0 port
-> 5 m 25 s to copy the file
-> sync operation takes forever (like 10 minutes)

Both the flash keys have a ntfs partition. I used to use fat but I'd tried ntfs to check whether I get some better performance.

The flash keys are auto-monted, this is the current situation:

/dev/sdc1 on /run/media/mik/6B52DA9C375A1D3B type fuseblk (rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096,uhelper=udisks2)

While copying operation is in progress, I can't find any warning/error in dmesg or with journalctl.

I'm running an up-to-date Archlinux:

Linux Okinawa 4.10.11-1-ARCH #1 SMP PREEMPT Tue Apr 18 08:39:42 CEST 2017 x86_64 GNU/Linux

And using on of the following:
- Nemo on Gnome3
- Nautilus on Gnome3
- cp from terminal
to copy the files.

I would like to get some help.
First: do you think that I have a problem? Or should I check something else?
Second: what can I do to get a reasonable situation?

Any help would be more than appreciated!
My best / MJ

tom.ty89

Member

Registered: 2012-11-15

Posts: 897

Re: Slow USB write issue

41000MB / (16min * 60s = 960s) = 42.7MB/s = 341.7Mb/s

While the theoretical maximum data rate of USB 2.0 is 480Mb/s (60MB/s). So it seems reasonable to me.

MajinJoko

Member

Registered: 2007-08-15

Posts: 84

Re: Slow USB write issue

It makes sense. Thanks!

I'm wondering now whether I could get a more "realistic" status of the copy process. At the moment, the copy itself seems to tooke 5 minutes, while the following sync need 10 minutes. Shouldn't it be a single process? Shouldn't I see a constant progress?
As it is now, what happen in Nemo is that the copy process seems very fast for the initial 50-60%, then the speed drops and it slows down until it completes.
Maybe the whole time needed is correct, but the output is annoying and not much helpful.

tom.ty89

Member

Registered: 2012-11-15

Posts: 897

Re: Slow USB write issue

I guess you can tune the dirty page ratio or so? Haven't really get to know about it. Here is a random search top result:
https://lonesysadmin.net/2013/12/22/bet … rty_ratio/

seth

Member

Registered: 2012-09-03

Posts: 51,143

Re: Slow USB write issue

Mounting "flush" will
man mount:

flush
If set, the filesystem will try to flush to disk more early than normal.  Not set by default.

sync
All  I/O  to the filesystem should be done synchronously.  In the case of media with a limited number of write cycles (e.g. some flash drives), sync may cause life-cycle shortening.

---

How to upload text · How to boot w/o GUI · Disable Windows Fast-Start! · Fix your xinitrc

mich41

Member

Registered: 2012-06-22

Posts: 796

Re: Slow USB write issue

41000MB / (16min * 60s = 960s) = 42.7MB/s = 341.7Mb/s

It was 4.1GB, not 41GB. So 4.3MB/s, well below USB 2.0 speed limit.

This being said, few megs per second isn't out of line for old/cheap/small pendrives.

Last edited by mich41 (2017-05-06 14:34:22)

tom.ty89

Member

Registered: 2012-11-15

Posts: 897

Re: Slow USB write issue

41000MB / (16min * 60s = 960s) = 42.7MB/s = 341.7Mb/s

It was 4.1GB, not 41GB. So 4.3MB/s, well below USB 2.0 speed limit.

This being said, few megs per second isn't out of line for old/cheap/small pendrives.

Oh right I miscalculated. (I actually wondered why it is that "fast" )