VMware's flagship product ESX Server and the infrastructure around it aren't quite good enough for the data centre, according to David Turner, vendor marketing and business development manager at IT consultancy IQ-SYS, formerly Interquad.

This is one of the first and rare cases of a vendor not endorsing VMware's products, whose market leadership and mindshare among end users is huge.

The consultancy and networking specialist, whose revenues reached over £35 million in its last financial year, sells only SWsoft's Virtuozzo, rather than market leader VMware's product. VMware's lead in the market is substantial but the reason why the distributor chooses to buck the market trend is clear, according to Turner.

He said that Virtuozzo's value "is in the server farm and data centre, where hardware virtualisation [such as that provided by VMware's ESX Server] doesn't add much value to I/O-intensive applications. People couldn't put multiple ESX Servers in a high throughput application," he said. Referring to applications such as Citrix server farms and databases such as Oracle, he said that "we get greater scalability with Virtuozzo."

Turner said the key is to maximise use, and that VMware has left a gap in the market which SWsoft has exploited. "VMware adds value when you're running multiple OSes - which Virtuozzo cannot do -- but virtualising a whole machine like that adds overhead. With Virtuozzo you're not doing that so you can get significantly more virtual machines on one box. SWsoft also has a management console that can manage those VMware VMs, so if you have both, they work together.

"VMware is good for test and development, and for consolidation of different servers. But on a greenfield site and Citrix server farms, which are all pretty much the same configuration, you don't have a requirement to support different OSes."

However, Turner said that there was "room for both vendor solutions to sit side by side in the same organisation, drawing maximum advantage from the benefits of virtualisation, although IQ-SYS will be concentrating on the applications at which Virtuozzo excels."