Large backups locks harddrive while running

[cederberg]

I perform daily backups with rsync to another partition on the same drive. (I know, I know, not the best solution...) From time to time these backups are quite large (in the 1-10 GB range) and naturally take quite some time.

However, while such a large backup is running, the harddrive is practically "locked up" and the system may become unresponsive. CPU usage remains very low (DMA enabled), so any activity only requiring CPU or network works perfectly, but as soon as the HD is accessed applications find themselves in long I/O waits.

Now, I've tried to lower the priority of the backups with nice, but it doesn't seem to affect the I/O problem. Is anyone out there aware of some method to force rsync make small I/O pauses, allowing other applications to get at least a minimum guaranteed throughput during the backups?

I'm planning to use Gentoo Linux for a production server, and while I can live with this for my desktop, it would be critical if the server went unresponsive during such a trivial thing as a backup...