Irvine-based disk drive maker Western Digital Corp. has acquired Arkeia Software Inc., a Carlsbad-based provider of backup software, on undisclosed terms.

Shares of Western Digital were up 5.4% during morning trading, to a market value of $11.49 billion.

Western Digital will fold Arkeia into its small- and medium-business unit, and expects the addition to boost its portfolio with products designed for the “larger SMB customers,” according to Western Digital’s Executive Vice President Jim Welsh.

Arkeia provides data backup software, as well as other services such as data de-duplication. Its products are used on more than 150 platforms, including Windows and Linux.

Arkeia, which also operates an office in Paris, does not release financial information. It received a $3 million equity funding in 2007 from Seventure Partners and the private equity arm of the Crédit Agricole S.A., both based in Paris.