1. A computer-implemented method for cache coherency, comprising: establishing one or more appliances, each defining a storage cluster; establishing one or more tenants spanning across said one or more appliances, wherein an application stores objects in file systems associated with said appliances and said tenants; establishing a global index (Gindex) including metadata relating to objects stored in association with said application, wherein each object is associated with a unique object identifier; replicating said Gindex to plurality of data centers supporting said one or more tenants; storing an original object at a first data center; storing a cached copy of said object at a second data center; aligning said cached copy of said object to said original object using metadata for said object from a local copy of said Gindex.