Comment 258 for bug 197762
Revision history for this message
| allisterbrizan (allisterbrizan) wrote Re: file transfers on USB flash key (pendrive) or USB HDD are slowing down with time | #258 |
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1b1ed1a
(Get the code!)
Please don't brush this aside as "poor performance". This is an issue in long disk activities. I notice this bug in both disk copies and dd.
I use dd quite frequently to clone disk images onto identical computers and very regularly have to copy these 75.4GB disk images. While i have not done a forensic investigation this is what i have noticed after facing this issue MANY times:
1. It definitely affects Ububtu 9.10, Ububtu 9.04, Ububtu 8.10, Ububtu 9.10UNR, Ububtu 9.10UNR. (It seems to be a bigger problem UNR distros)
2. In Ubuntu 9.04 i get this slowdown in approximately 25% of the dd clones i do (2 out of 7 computers this weekend). Canceling and restarting the computer don't fix this issue.
Note: For dd clones i boot off a USB stick and invoke dd in a terminal window. The drive images copy from a file on a NTFS drive to /dev/sda or vice-versa.
3. Using the computer makes this bug less likely to happen. (I truly believe this has something to do with efficient power consumption or reducing disk writes.)
4. The read/write rate decreases over time in a predictable manner. A dd clone which works normally copies the 75.4GB file in 3054s give or take 10. If the bug occurs it takes approx. 23200s.
This is a real problem. I will do some proper testing and analysis based on suggestion.