While the worldwide market for storage software grew 8.6% from a year earlier, to US$2.5 billion, revenue from storage software dropped 3.2 percent at EMC and slipped 1.8% at Symantec Corp.

EMC remained the market leader, with storage software sales of $654 million and a 26.4% share of the market, but its share fell from 29.6 percent in the second quarter of 2005. But the vendor’s share has been sliding since 2004, in line with previous IDC figures.

Second-place Symantec saw sales drop to $468m and its share of the market slide to 18.9% from 20.9% last year. It acquired storage software specialist Veritas in July 2005, which was reflected by comparing Symantec's latest storage software revenue with combined figures for the two companies before the merger.

IBM storage software sales grew 40% year on year to $31m, taking its share of the market to 12.5 percent, from 10.1 percent a year earlier.

Network Appliance, in fourth place, grew even faster: its revenue from storage software jumped 57.5% to $222m, giving it 9% of the market, up from 6.2%. This allowed it to overtake HP, where storage software revenue slipped 2.7% and market share dropped to 5.7% from 6.3% a year earlier, said the research firm.

IDC also said this is the 11th consecutive quarter of growth in storage software sales. It attributed much of the growth to demand for storage replication systems, where sales grew 13.2% year on year, as companies make good on their disaster recovery and business continuity planning.

Demand from archive and hierarchical storage management software grew 32%, but from a much smaller base.