The total worldwide disk storage systems market grew 9.9 percent to US$5.6 billion in the second quarter of this year compared to the same quarter last year, according to IDC. The growth was the highest year-on-year growth over the last eight quarters.

In a further indication as to market growth, total disk storage, measured in petabytes grew 59.3 percent to reach 457 petabytes in the second quarter. IDC defines the total disk storage systems market as the combination of internal and external systems.

In the total worldwide disk storage systems market, Hewlett-Packard maintained its lead in the second quarter of 2005 with a 23.5 percent revenue share followed by IBM with a 20.5 percent share. EMC held the third position with 14.4 percent, then Dell with 8.3 percent and Sun Microsystems Inc. with 6.1 percent. Of the top five vendors, Sun was the only one to forfeit market share, with a fall in revenue year-on-year of 10.4 percent.

The storage market offers opportunities as organisations become more dependent on "the value of their business information," said Brad Nisbet, programme manager in IDC's Storage Systems programme.

In the external disk storage systems market, overall factory revenue grew 8.6 percent year on year to $3.8 billion. EMC cemented its lead with a 21.2 percent revenue share, followed by HP with 18.8 percent and IBM with 13.8 percent. Dell was in fourth position with 8.3 percent, displacing Hitachi Data Systems, which fell back to fifth position and a 7.3 percent share.

Dell's success is in large part due to its partnership with EMC, which allows Dell to resell co-branded Dell/EMC storage systems. In the IDC study, the analyst attributes revenue to the seller or brand of the product, not the manufacturer. For instance, Hitachi's sales in the study don't reflect the company's OEM sales to both Sun and HP.

Dell had the largest year-over-year growth in external disk storage systems with 27.1 percent. HP and IBM also had double-digit growth, of 13.7 percent and 13.4 percent respectively. The uptick was not surprising in HP's case because the company had an unexpectedly weak second quarter in 2004, IDC noted. The top five vendors accounted for close to 70 percent of the external disk storage market.

IDC defines the total network storage market as the combination of NAS (network attached storage) with Open and iSCSI SANs (storage area networks). The market grew to nearly $2.5 billion, an increase of 16.1 percent year-over-year growth. EMC's still the dominant player with a 27.9 percent revenue share, followed by HP with 21.3 percent. However, Dell and IBM posted the strongest year-on-year revenue growth with 33.2 percent and 22.9 percent respectively.

Turning to the NAS market, which grew 9.5 percent to $475 million revenue. There were only two players of note - EMC was the leader with 40.2 percent revenue share, followed by Network Appliance with 35.2 percent.

The Open SAN market, including iSCSI, topped $2 billion in revenue, growing 17.8 percent year on year. EMC and HP effectively tied for first place, EMC with 25 percent revenue share and HP with 24.8 percent. IBM was in third position with a 14.3 percent share.