queue for copying and moving files

[Allan Sandfeld Jensen]

On Saturday 18 October 2008, Thorsten Gensler wrote:
> Thiago Macieira wrote:
> > I think you're asking the wrong people. The kernel developers should be
> > doing the I/O scheduling, not us.
> >
> > Remember that KDE (much less KIO) does not control all I/O.
>
> I don't think that I'm asking the wrong people. I talk about fileoperations
> like this example:
> 1. action
> mv /home/user/FILE1 /media/externHD/FILE1
>
> 2. action
> mv /home/user/something/FILE2 /media/externHD/FILE2
>
> mv is only for explain the operation. I mean mv is done in the Desktop
> Environment, not in the shell.
>
> The second action should be in this queue because it's an operation on the
> same hd. At the moment it would be started two instances of moving the
> files and it is slower than waiting for the end of action one.

The problem is we have to make assumptions of the disk-configuration. For 
instance if the directories are in different mounts, then they would be 
faster in parallel, if the mounts are different hardware, but not if they 
share disks. If the disk is RAID-1 mirrored, then reads are faster in 
parallel, but writes are not.

Such optimization has to be done by the kernel (or hardware*), because it is 
the only place with enough information to do the optimizations.  

*Note that if you buy yourself a SCSI or SAS disk, then the buffer on the disk 
will do this kind of operation reordering for you.

`Allan