Storage startups 3PAR and Equallogic filed IPOs Tuesday in a market that is heating up for storage IPOs.

IPOs are all the rage in the storage arena. This year alone, 3PAR competitor Compellent, Data Domain and Voltaire filed for IPOs. They joined Riverbed, Isilon and Mellanox, who filed for IPOs last year and VMware, who went public Tuesday.

"With the successful VMware IPO yesterday and the recent Data Domain IPO, we may be seeing a shifting trend here of companies who have filed and or IPO'd without being profitable to companies that are either already profitable, or, at least well on their way to being self-sustaining businesses without the need to race to the IPO exit window," says Greg Schulz, senior analyst for StorageIO.

3PAR, the manufacturer of a storage array that supports utility computing, is hoping to raise US$100 million (AU$122.44 million) in common stock. 3PAR's InServ Storage Servers allow consolidation of the storage resources on the network. Its software, based on the proprietary InForm operating system, supports capacity management, thin provisioning and remote copy ability.

3PAR expects to use the proceeds from the offering for working capital to repay outstanding debt.

The company, which was founded in May 1999, counts among its customers Credit Suisse, Dow Jones and Verizon Business. Its products compete with those from EMC, IBM and HP.

EqualLogic, a company that makes iSCSI storage arrays, also filed an S-1 with the Securities and Exchange Commission (SEC) Tuesday. The number of shares and their value has not yet been determined.

EqualLogic PS Series iSCSI storage-area networks come with thin provisioning and replication capabilities. The company's customers include Dartmouth College, Fortis Fund Services and Lockheed Martin, among others. EqualLogic declined to comment on the IPO, citing its involvement with the SEC registration period.