Doing some benchmarking on virtual machines, I discovered on fast drives that virtio drivers are about 10% faster than emulated SATA drives for the SAME hardware.

     I had erroneously assumed SATA would be faster because it supported hdparm read-ahead where virtio does not support this parameters, but it turns out that the Linux kernel has demand read-ahead that detects sequential reads and automatically reads ahead and prefills buffers when it detects this. That nullifies this advantage and thus the reduction in interrupts and system calls of virtio provides better performance.

     As a consequence, I am going to take the web, mail, and uucp servers down briefly around 11pm tonight to change it’s virtual disks from SATA to virtio.