Pure Storage, last valued at $3 billion, is going public but it's losing a lot of money

Pure Storage, the flash storage startup valued at $3 billion by private investors in 2014, filed for an IPO on Wednesday.

The company will list under the ticker symbol PSTG, and Morgan Stanley will lead the IPO.

Pure Storage is a company that offers flash storage for other companies to use in their data centers. Flash drives provide much better performance and speed, although it's more expensive than traditional hard disk drives.

The IPO filing has been expected for some time now, especially after Pure Storage hired the former Google finance exec Tim Riitters as its CFO last year.

Despite its high valuation, Pure Storage's S-1 revealed that the company's losing a lot of money. Last year, it reported a net loss of $183.2 million, while it made $174.5 million in sales.

Investors looking for good news could focus on Pure's growth - sales in 2014 increased about 4x from the previous year, and in the first quarter of 2015 it had sales of $64 million, putting it on track to do more than $250 million in sales this year.

The bulk of its loss came from sales and marketing, as it spent more than $152 million on it last year.

The company will roll out a dual-share class structure, which will allow early investors and other insiders to retain control over the company even after the IPO. These structures have recently become common in the tech industry, used by Google, Facebook, Box, and others. The largest individual shareholder in the company is founder and chief technical officer John "Coz" Colgrove, who owns 8.5% of the company.

So far, the company has raised $470 million in venture funding from investors such as T. Rowe Price, Wellington Management, and Greylock Partners.