I'm running Linux Mint 15 KDE edition, and my home directory is on an encrypted

When I transfer between a USB2 hard drive, and the internal hard drive in my laptop, Dolphin, (or perhaps the Linux Kernel itself, I'm not really sure which), will read from one drive, without committing anything to the destination, (it reads into the write cache), and then when it starts purging the write cache to the destination, it stops reading from the source drive. Since the one hard drive is USB2, this reduces the average transfer speeds from the ~45MB/s that the USB2 drive is capable of, to around ~20MB/s.

Is there some way around this, to cause it to write at the same time it's reading?

Does it behave differently when you use e.g. cp or rsync?
I would have guessed that this is low-level IO which is performed by the operating system, not by KDE. But I maybe wrong, or there may be something KDE does which prevents it from working as it should.

Try with other tools, that will tell more.

Greetings,
Sven

scummos wrote:Does it behave differently when you use e.g. cp or rsync?
I would have guessed that this is low-level IO which is performed by the operating system, not by KDE. But I maybe wrong, or there may be something KDE does which prevents it from working as it should.

Try with other tools, that will tell more.

Greetings,
Sven

I can't really do any easy tests with "cp", so I used "pv" instead. It had the same effect, with transfers running burst speeds during reads, and dropping to KiloBytes on writes, with averages well below what the drive should be capable of.

I've tried turning off drive caching with

Code: Select all

hdparm -W 0 /dev/sdX

But I'm lead to believe this has to do with the drive's internal caching, and not the kernel in-RAM caching.

Have you tried using iotop to monitor I/O activity? It will show kernel level components as well, such as file systems and the block subsystem - which will allow you to determine where to begin looking to adjust this behaviour.