Always paid attention to another oddity in the disk system in Linux:
When active drives, e.g. when copying a file (no matter between different disks or not) the CPU usage grows up very much (most of it is in iowait, usually completely focused on one core) and the system subjectively begins to work more slowly, becomes less responsive.
The winchesters I have SATA2 in the BIOS before there was mode IDE to SATA, recently put AHCI, no difference noticed)
Stone is a dual-core Phenom II x2 555.
Tested hdparm'ω the speed of linear reading — to a new terabaytnye 100 MB/s, for the old screw on 320Gb — 70 MB/s.
I don't know how these values are normal.
A large file copy from the old screw on new — about 50 MB/s.
System is ArchLinux x64.
I would like to hear the opinions of those better versed in working with Linux disks.