Software plans for making high-end computing jobs less susceptible to system crashes are ratcheting ahead, with improvements coming to products for Linux and Windows. The products fit into the realm of "clustering", in which one server can take over for another that crashes. When it works--and it's difficult to create and install such software--it can mean that back-end server failures won't disrupt activities such as a bank teller depositing a check, an eBay customer bidding for a trinket or a car dealership recording a new purchase. But clustering is expensive and difficult to accomplish. Microsoft initially hoped clustering would give the company an edge on its Unix server competition, but the effort took years longer than hoped, with clustering still only an option for high-end products. Even in the Unix market, where software developers have had more time to get the technology working, it's relatively rare. And smaller companies such as Mission Critical Linux that are trying to sell clustering products must face established leaders such as Veritas. In a recent survey, IDC analyst Jean Bozman found that clustering still is comparatively rare. Nearly half of the companies she surveyed had clustering set up on less than a tenth of their servers. But adoption is growing for important server tasks. Companies will spend about $6bn (£4.2bn) on clustering products this year, Bozman predicted, with about $4bn of that for Unix systems. In 2005, she predicted, spending will increase to $14bn, with Windows growing faster but still accounting for less than half the market. Products to make clustering more useful are creeping along. NSI Software on Wednesday released a new version of its GeoCluster software, which lets one Microsoft Windows server take over for another in a different location. That's useful to protect against fires, earthquakes or other local disasters. The new version 4.1 doesn't just support the underlying operating system but extends the protection to Microsoft's Exchange email server software. It also ties in with Microsoft's Active Directory, which lets a server keep track of numerous features of a computer network, such as user passwords and access privileges. Geocluster's product costs $4,495 per server, the company said. Another company hoping to profit from clustering is Steeleye, whose LifeKeeper product was spun off from NCR in 1999. Steeleye supports Windows, Linux and Sun Microsystems' Solaris version of Unix. Like NSI, Steeleye is pushing its clustering support to higher-level software. Its newest product, SteelEye Disaster Recovery, includes support for Microsoft's Exchange email software, Internet Information Server Web server software and SQL Server database software. It also supports Oracle database software, SAP's high-end business and accounting software and other packages. The Disaster Recovery product currently runs only on Windows servers, but Linux support is expected in early 2002, the company said. The product costs a minimum of $9,500 per site. See the Linux Lounge for the latest GNU/Linux and open source headlines. See the Software News Section for full coverage. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the Linux lounge forum Let the editors know what you think in the Mailroom. And read other letters.