The rise of virtualization software made by companies like VMware and Microsoft has forced hardware companies into drastic action.

Hewlett-Packard, for example, said it was spending $360 million in cash on LeftHand Networks, a company that makes storage software which plays well with virtual servers. The LeftHand code stretches across the disk drives found in standard servers and turns them into what looks like a single, large system for storing data. By using everyday disk drives for this purpose, companies can avoid constructing a separate storage network typically made up of expensive, complicated equipment.

(Virtualization refers to technology that creates a virtual version of an operating system and its associated applications. The technology reduces the costs of running software in a large enterprise by letting more software run on each physical machine.)

The simplified approach to storage proves attractive to customers dealing with the large number of virtual servers created when a product such as VMware is used to run multiple operating systems on a single physical machine. They’d rather keep the server and storage systems as part of a single, similar network. And satisfying this desire could be a big win for H.P., since it’s a major player in both the virtualization and storage markets.

H.P.’s deal, announced today and expected to close during the company’s first quarter, follows a number of similar purchases by rivals.

In January, Dell completed a $1.4 billion acquisition of start-up EqualLogic, gaining access to storage hardware and software that also complements virtual servers. That same month, I.B.M. acquired Israel’s XIV for an undisclosed sum. I.B.M. now offers the XIV Storage Systems, which turns numerous low-cost disks into a large unified storage unit.

Companies like EMC and NetApp are tackling this technology as well.

“Dell was the first to really substantiate the value and possibility here by spending a lot of cash,” said Steve Duplessie, an analyst at the Enterprise Strategy Group. “Now, everybody has to have a play.”

To geek out for a moment, all of the storage systems here deal with a protocol known as iSCSI, or Internet Small Computer System Interface. Support for this technology has been building over recent years as it allows storage systems to make broader use of Ethernet networking technology.

In the past, customers would often need to purchase hulking and pricey storage hardware to handle tough jobs related to databases and other complex business software. Thanks to iSCSI much of that work can be accomplished on cheaper systems more similar to existing gear.

As it turns out, the iSCSI technology can keep track of virtual servers moving around physical systems better than the other storage systems as well.