EMC maintained its lead over NetApp and IBM in an external disk storage systems market that saw a slight (just under 1 percent) worldwide decline in revenues in the first quarter of 2013, totaling around $5.9 billion, according to IT research firm IDC's Worldwide Quarterly Disk Storage Systems Tracker.

EMC boasted 30.4 percent revenue share during the first quarter, followed by NetApp and IBM with 14.9 percent and 10.9 percent respective market share. Hitachi and HP, meanwhile, finished the quarter in a statistical tie for the No. 4 position with 8.9 percent and 8.5 percent, respectively, of external sales. IDC declares a statistical tie in the worldwide disk storage market when there is less than 1 percent difference in the factory revenues of two or more vendors.

The network area storage (NAS) market declined 2.2 percent year over year, led by EMC with 39.6 percent revenue share and followed by NetApp with a 37.4 percent share, according to the report.

In the total worldwide disk storage systems market, EMC finished in the top position followed by HP with market shares of 23.2 percent and 15.5 percent, respectively, followed by Dell with 13.9 percent, IBM with 12.1 percent and NetApp with 11.4 percent. EMC's revenue in this market approached $1.8 billion, while HP recorded $1.2 billion in revenue in the first quarter of 2013. Other vendors represented 23.9 percent of the market, posting revenues of $1.8 billion.

"Reduced demand within developed markets caused global sales of external disk systems to fall slightly during the first quarter of 2013," Eric Sheppard, research director for storage at IDC, said in a statement. "Emerging markets drove growth within the global market but this was not enough to offset declines elsewhere. Independent storage suppliers were better positioned to capitalize on this new level of demand than their competitors, some of whom are currently working through product transitions and declining server sales."

The total open networked disk storage market—NAS combined with non-mainframe storage area network (SAN)—grew slightly (0.4 percent) year over year during the quarter to just over $5.1 billion in revenues. Again, EMC continued to maintain its leadership in the total open networked storage market with 33.4 percent revenue share, followed by NetApp's 17.1 percent revenue share.

In the open SAN market, which grew just 1.3 percent year over year, EMC was once more the leading vendor with 31.2 percent revenue share, followed by IBM in second with 12.6 percent market share and HP and Hitachi tied for third with 10.8 percent each.

For the purposes of this report, IDC defines a disk storage system as a set of storage elements, including controllers, cables and in some instances host bus adapters, associated with three or more disks. A system may be located outside of or within a server cabinet, and the average cost of the disk storage systems does not include infrastructure storage hardware, such as switches, and non-bundled storage software.