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I have a Core 2 Duo T8100@2.1GHz with 3GB RAM. After some time using XUbuntu 10.10 on an 8GB stick I decided to switch to 12.04 and put it onto a 32GB stick (Transcend).

I use an EXT4 with no journalling, noatime etc set. /tmp and /run is using tmpfs.

And it is REALLY slow. MUCH slower than the old Xubuntu on the 8GB stick. Starting takes minutes, all applications "fade" because they respond too slow.

I first thought that the NVidia graphics card is responsible for this, because there seem to be some known problems with that. Doing the adjustment (uncheck the sync checkbox) did not help.

I believe the root cause is that the access to the USB stick is extremely slow. Running the read benchmark of the disk utility then brought the message "disk is too slow to benchmark"!

BUT: When I do the same benchmark with the live CD I get around 20MB read performance and have a very responsive system!

So how can I find out what is going one here?

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I wonder if this is because there are a load of dirty pages being written back and this is causing the CFQ I/O scheduler some issues on a slow device. Switch the I/O scheduler to deadline and see if it helps. For example, if you are using block device /dev/sda then use:

echo deadline | sudo tee /sys/block/sda/queue/scheduler

Maybe that will improve things.

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But can this explain the huge difference between the results of the read benchmark from live CD vs. from the usb stick itself? In both cases the system was idle.... –  user85340 Aug 24 '12 at 17:17
    
Why don't you benchmark the USB sticks to see if there is any speed differences between the two. Insert a USB stick into a Linux box and see which device it appears on, e.g. /dev/sdb. Then read 1GB from the device using dd and see how long that takes, e.g. sudo dd if=/dev/sdb of=/dev/null ...and compare both USB sticks. Maybe the root cause is a slower USB stick. –  Colin Ian King Aug 24 '12 at 18:24
    
i did that with the disk utility of the live cd - the new stick is faster. so the hardware seems to be okay. is there any way to monitor the traffic between computer and usb stick? –  user85340 Aug 24 '12 at 18:58
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