[2] As of May  2009[update] Oracle Corporation agreed to acquire Virtual Iron Software, Inc., subject to customary closing conditions.

[4] Virtual Iron software ran unmodified 32-bit and 64-bit guest operating systems with near-native performance[citation needed].

However, the use of a virtual-storage access model leveraged SAN storage to create a fault-tolerant iSCSI or Fibre Channel based cluster of virtual nodes.

Native virtualization allowed for unmodified guest operating systems and had the advantage of hardware advances for better performance.

From our discussions with a broad range of users, they simply do not want to roll out modified OSs unless the trade-off is heavily in their favor.