Quoting from the 4Blox official announcement:
4Blox, Inc., dedicated to improving iSCSI SAN performance, today announced that it has teamed with two leading technology vendors, Red Hat, the world’s leading provider of open source solutions, and VMware, in its efforts to build a strong network of industry partners to ensure delivery of high-performance storage solutions that meet market requirements.
…
The company has also joined VMware’s Technology Alliance Partner (TAP) program. Virtualization is driving a data center infrastructure refresh, but with virtualization comes increased host CPU resource constraints associated with storage protocol processing. 4Blox’s software approach to iSCSI acceleration can be dynamically enabled in one or more Guest OSes offering storage system vendors a more flexible and lower-cost alternative to hardware-based offload processing solutions.
iSCSI-based Storage Area Networks (SANs) experience severe system performance degradation when used on standalone servers with large numbers of users or with bandwidth intensive applications – like backup and video, and on virtualized servers where CPU resources are constrained by multiple Guest OSes. The CPUs deployed in typical storage subsystems are quickly overloaded with iSCSI processing and 10GbE connections can exhaust host CPU processing with even a small number of users…
4Blox produces high performances iSCSI target and initiator called 4Mezzo. The company will probably work with VMware to certify and include 4Mezzo in upcoming versions of ESX Server.