On Tue Oct 07, 2014 at 12:36:19PM +0200, P. Gautschi wrote:

quoted

What does the SMART info show for the drives - are there any reallocated
blocks? A large number of those scattered over the disk would certainly
cause seeking for both reads and writes.

I will check the SMART this evening but I don't think that this is causing
the seek. The sound is very constant and for the whole time of syncing  
the array.
I will also run a dd on the disk to compare.

quoted

It's also worth checking whether there's anything else that would be
accessing the disks in the background (monitoring/indexing/etc).

Unlikely because I have not yet created a filesystem after setting up  
the RAID4.

quoted

I can't think of anything else that would be causing reads to seek - SMR
disks or write-intent bitmaps would only affect writes.

Exactly

Is there any way or tool to monitor all disk read/write commands - not only
the count or amount but every access with LBA and length?

You can do:
    echo 1 > /proc/sys/vm/block_dump

That will write out all disk IO to the kernel log (process ID,
read/write and block offset only though). It can be very verbose,
especially if you have a lot of other things running on the system, but
you should be able to grep out the necessary lines. Echoing 0 will
switch it back off again.

Otherwise there's probably ways to get more specific results via the
kernel auditing system, but that's nothing I've played with.

Cheers,
    Robin
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