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gerdOffline
Post subject: massive USB stick perfomance problems  PostPosted: 30.07.2011, 22:38



Joined: 2010-09-13
Posts: 94

Status: Offline
Test case: copy a 1.9gb aptosid iso to 8gb usb stick (fat32, usb2).
Test system is a c2d with 4gb ram, up to date kernel and software. Music plays in background, cpu load some % and system load at 0.25.

Tested it with 2 different sticks but same effects.
The USB stick have a max write rate of 12MB/s. A test under windows (on another pc) reached that with that iso.

      Code:
 time cp aptosid-2011-02-imera-kde-full-i386-amd64-201107131633.iso /media/8GB/^C
real   11m35.014s
user   0m0.028s
sys   0m3.298s


But to the performance impacts:
cp starts with 12MB/s transfer rate, but after some 100MB it breaks in. The load reaches 7 (!), iceweasel freezes complete for minutes, starting software that is not in ram freezes also.

(i tested it also with other linux distributions but also bad speeds and heavy loads)

Any ideas? The log files are without error messages.

edit: Same freeze and load effects when source is a virtual device
      Code:
 dd if=/dev/zero of=/media/8GB/d bs=128k count=16000
16000+0 Datensätze ein
16000+0 Datensätze aus
2097152000 Bytes (2,1 GB) kopiert, 264,871 s, 7,9 MB/s


edit2:
I did same tests on ext. usb hdd. All was fine, no problems.
It seems that only usb sticks do have this problem.
 
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finottiOffline
Post subject: RE: massive USB stick perfomance problems  PostPosted: 31.07.2011, 14:31



Joined: 2010-09-12
Posts: 294

Status: Offline
I had the same problem. I think I've posted here a while ago with no responses... I hope you have more luck.

I remember reading somewhere that it might be related to the scheduler, but my memory is not very good and I could not find the reference anywhere.

Good luck,

Luis
 
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