I've got a ubuntu (server kernel) on a amd x4, 4gb ram, 2x seagate sata 1 tb disks for testing virtual machines and the write performance is very slow. The two disks are in a software raid1 array, one small boot ext3 partition, 10gb system partition and the rest is a xfs partition (about 980) gb for data (virtual machines).

If I'm copying files from the virtual machine to the host with rsync or scp the copy frequently stalls or goes at about 1mb/s. What's wrong?

I've tried disabling barriers on xfs, increased logbufs, allocsize, but it seems nothing helps.

The strange thing is that await (for example during copying) for sda is usually under 100, while for sdb is around 400.

Any ideas on what could be wrong / what could I do to improve this setup?