Insight Venture Partners, Jeff Horing's New York investment firm, and Citrix Systems, a publicly-traded, Fort Lauderdale-based software service company, have made new investment agreements with Philadelphia-based PHD Virtual Technologies, a backup provider for virtual-machine software systems, according to a joint statement.

Insight and Citrix won't say how much they're investing. "We do several deals a quarter," Citrix spokesman Eduardo Fleites told me. "PHD Virtual Technologies (is) a strong partner and attractive investment opportunity," said Andy Cohen, Citrix' senior director of strategic development. PHD recently rolled out Backup for Citrix XenServer, the latest version of the Philadelphia firm's esXpress backup service.

PHD boss Thomas Charlton told me the firm employed 20 when he joined last winter, and plans to hire "at least" 20 more, mostly salespeople, this year. PHD competitors include Veeam Software, of Columbus, Ohio, and VMWare, Palo Alto.

The company's name traces to founder Ron McKelvey and his colleagues; it's an in-joke that they didn't have doctorate-level software developers when they started the firm in 2006: The veteran programmers had "virtual Ph.D.s," Charlton says. Charlton previously headed network-emulation provider Shunra Software, which is backed by Insight and by Carmel Ventures of Israel. Before that he ran VoiceGenie Technologies, Toronto, another Insight-backed firm.