Seagate Technology is stepping up with an aggressive plan to boost shareholder value.

The disc-drive giant said it will increase its quarterly dividend by 25 percent, from $0.10 to $0.12 per share.

At the same time, Seagate’s board of directors has authorized the repurchase of up to an additional $2.5 billion of stock — equal to 23 percent of its current market capitalization — over the next 24 months. On Tuesday the stock price was down about 27 percent from its high in November 2007.

Seagate said it will fund the share repurchase through a combination of cash on hand, future cash flow from operations, and potential alternative sources of financing.

The repurchases may be made through a variety of methods, including open-market purchases, privately negotiated transactions, block trades, accelerated share-repurchase transactions, or any combination of those.

Seagate’s buyback stands out not only for its magnitude. Surprisingly, few companies have announced share repurchases since the stock market’s big falloff began in November.