In order to have a better idea of what is the IO performance on an Internet server here is a small tool that would make relative good IO(disk performance) tests.
apt-get install iozone3
iozone -I -T -t 5 -r 64k -s 2G -i 0 -i 1 -i 2 -c -e
The results are easy to read.
Here is another example brought by a friend:
iozone -I -i 0 -R -l 3 -u 3 -r 16k -s 10000m -F /mnt/DATA/io1 /mnt/DATA/io2 /mnt/DATA/io3
This one I use for write Tests only. It creates 3 files around 10G each and only writes them. Record size is 16k this Time and it uses direct-io for the operation.