VMware Knowledge Base (KB) - Linux 2.6 kernel-based virtual machines experience slow disk I/O performance (2011861)

If you're using Linux 2.6 kernel-based virtual machines and you're experiencing slow storage performance as compared to physical hosts, the might be a problem with the I/O Scheduler. As of the Linux 2.6 kernel, the default I/O Scheduler is Completely Fair Queuing (CFQ).

The default scheduler will affect all disk I/O for VMDK and RDM-based virtual storage solutions. In virtualized environments, it is often not beneficial to schedule I/O at both the host and guest layers.

--> The rest is on the blog : http://www.ntpro.nl/blog/archives/2400-VMware-Knowledge-Base-KB-Linux-2.6-kernel-based-virtual-machines-experience-slow-disk-IO-performance-2011861.html