Major institutional investors are ramping up their investment activity in the self-storage sector, even as public REITs continue to pull off the biggest deals. [Editor’s Note: This story was updated Thursday morning May 19th with news of the Sovran Self Storage deal.] This morning Sovran Self Storage Inc., a self-storage REIT, announced it has agreed to acquire LifeStorage LP, a privately-owned operator, for $1.3 billion, payable in cash.