High iowait when copying large files in Linux

Question

linux

I always paid attention to one oddity in the work of the disk system in Linux:
When actively using disks, for example, when copying a file (it doesn’t matter whether it is between different disks or not), the processor load increases very much (most of it falls on iowait, usually one core is completely occupied) and the system subjectively starts to work more slowly, becomes less responsive.
I have SATA2 hard drives, I used to have IDE mode for SATA in the BIOS, I recently set AHCI, I didn’t notice the difference)
The stone is a dual-core Phenom II x2 555
. 320GB - 70 MB / s.
I don't know how normal these values ​​are.
Copying a large file from an old screw to a new one is about 50 MB/s.
System - ArchLinux x64.

I would like to hear the opinion of those who are better versed in the work of Linux'a with disks.

Answer 1

This is fine. Don't sweat it.

Answer 2

If you copy something large from the system or to the system screw or to the screw (s) where your $HOME is located, then it is quite logical that the system will become subjectively slower.
A large iowait is also a completely logical thing, as a rule, it is the higher, the more extents (read: the more fragmented) the files are.
When I copy files on a separate screw, the system does not become noticeably slower at all.