Fusion-io has struggled with losses since its initial public offering in 2011, but SanDisk sees its technology as a major component for its own lineup of storage products. SanDisk is using its NAND memory chips to build and sell its own solid-state drives. The flash drives offer higher margins than SanDisk's traditional business of selling memory chips for smartphones and cameras.

"(SanDisk) was already positioning the company as more of a enterprise storage company. ... What the Fusion-io deal does is it enhances that significantly," Cross Research analyst Steven Fox said.

The deal follows a trend toward vertical integration in the storage market, with chipmakers buying smaller companies with specialized technology.

Fusion-io does not buy chips from SanDisk but it will after the deal is complete, SanDisk Chief Executive Officer Sanjay Mehrotra said in an interview.

"Vertical integration is really key to winning in the enterprise storage market," Mehrotra said.

Solid-state drives, or SSDs, are faster than traditional hard-disk drives and while they are still more expensive than traditional drives, they are increasingly being built into laptop PCs.

Flash drives are also being adopted by data centers, a market where SanDisk competes with rivals such as Western Digital Corp WDC.O.

SanDisk's offer of SUD 11.25 per share represents a premium of 21 percent to Fusion-io's Friday close but is 40 percent less than Fusion-io’s IPO price of USD19 in 2011.

Fusion-io's shares were up 23 percent at USD 11.45 on Monday, suggesting that some investors expect a higher offer.

Nandury Summit Research Partners analyst Srini Nandury said rival bids were unlikely since other storage companies, including Western Digital and Toshiba Corp 6502.T, bought SSD makers last year. (Full Story) (Full Story)

SanDisk's SSD business has been growing at a scorching pace. Revenue from SSDs jumped 61 percent in the first quarter, accounting for 28 percent of revenue.

Fusion-io, whose customers include Apple Inc AAPL.O and Facebook Inc FB.O, is SanDisk's fifth acquisition in enterprise storage, the most recent being its USD 307 million purchase of SMART Storage Systems last July.

Fusion-io, which employs Apple co-founder Steve Wozniak as chief scientist, has reported a loss for five quarters in a row.

It helped pioneer high-end solid-state storage technology but struggled to find customers beyond a few large companies running cutting-edge data centers.

"It's leading edge. It's a question of someone being able to harness that ... and drive it to profitability," said Fox of Cross Research.

SanDisk expects the deal, likely to close in the third quarter, to add to its adjusted profit in the second half of 2015. SanDisk's shares were up 3.70 percent at USD 102.11 on the Nasdaq on Monday.