Patent ID: 8281181

Claim:
A dispersed storage (DS) unit comprises: a plurality of memory devices that includes a first set of memory devices that are continually active and a second set of memory devices that are selectively active, wherein the first set of memory devices stores a plurality of first encoded data slices having a rate of retrieval in a first interval retrieval rate range and the second set of memory devices stores a plurality of second encoded data slices having a rate of retrieval in a second interval retrieval rate range, wherein a first encoded data slice of the plurality of first encoded data slices is a first encoded data slice of a first set of encoded data slices and a second encoded data slice of the plurality of second encoded data slices is a first encoded data slice of a second set of encoded data slices, and wherein the first set of encoded data slices is a dispersed storage error encoded representation of a first data segment and the second set of encoded data slices is a dispersed storage error encoded representation of a second data segment; and a processing unit operable to: determine when to activate a memory device of the second set; when the memory device is to be activated, activate the memory device to produce an activated memory device; retrieve an encoded data slice of the plurality of second encoded data slices from the activated memory device to produce a retrieved encoded data slice; determine whether the retrieved encoded data slice has an error; and when the retrieved encoded data slice has an error, initiate a rebuilding function to rebuild the retrieved encoded data slice producing a rebuilt encoded data slice.