Patent ID: 9483539
Filing Date: 2016-11-01
CPC Classification: G06F,H04L

Claim Text:
1. A method comprises: to determine whether a copy of data that is cached in local memory of a first device of a distributed storage network (DSN) as a plurality of sets of encoded data slices is up to date, sending, by the first device, read-if-revised requests to storage units of the DSN regarding the plurality of sets of encoded data slices wherein a read-if-revised request of the read-if-revised requests includes a name of the data and a local revision number, wherein the data is divided into a plurality of data segments, wherein the plurality of data segments are dispersed storage error encoded into the plurality of sets of encoded data slices, wherein each of the storage units stores a different encoded data slice from each set of at least some of the plurality of sets of encoded data slices to produce a different portion of the data and wherein one of the read-if-revised requests includes slices names for the encoded data slices of the different portion of the data and corresponding local memory revision numbers; determining, by a storage unit of the storage units, whether each revision number of stored encoded data slices of a corresponding different portion of the data is a more recent revision number than the corresponding local memory revision numbers; when one of the revision numbers of the stored encoded data slices of the corresponding different portion is the more recent revision number than the corresponding local memory revision number, sending, by the storage unit, a read response that includes the stored encoded data slice of the different portion having the more recent revision number to the first device; and when the revision numbers of other stored encoded data slices of the different portion are not the more recent revision number than the corresponding other local memory revision numbers, sending, by the storage unit, a read response that includes an indication that, with respect to the other stored encoded data slices, the corresponding other encoded data slices cached in the local memory are a current revision level.