After September 11 and Hurricane Katrina, companies started asking what would happen if their main office went dark. Double-Take Software had an answer. Its software copied every change on a business's key servers to a second machine, across the hall or across the country, as the changes happened. If the first server died, the second could take over. In December 2006 the company went public, calling itself the leading supplier of replication software for Microsoft servers.

Fifteen Years as NSI

The company began in New Jersey in 1991 as NSI Software. It released its replication software in 1995 and spent a decade improving it with customer feedback. The product sat on the server, watched for changed files and sent only those changes to the backup. That kept the copy current without heavy network traffic. NSI moved to Southborough, Massachusetts, and in July 2006 renamed itself after its product. The bet was that smaller companies wanted disaster recovery without a mainframe budget.

From DBTK to Thoma Bravo

Double-Take priced at $11 a share in December 2006 and began trading on Nasdaq under DBTK. It sold mostly through resellers and partners, and its focus on Windows servers fit the market as virtual machines spread. In May 2010 it agreed to be bought by Vision Solutions, a company controlled by the private equity firm Thoma Bravo, for $10.55 a share in cash. The deal closed that summer, and the stock left Nasdaq.

Cover: Reflections—Venice, Alfred Stieglitz. Art Institute of Chicago, public domain. Chosen for a reflection on water (a live copy).