Utilizing fast memory devices to optimize different functions

A computing device comprising:

• an interface configured to interface and communicate with a distributed storage network (DSN);
• memory that stores operational instructions;
• and
• a processing module operably coupled to the interface and to the memory, wherein the processing module, when operable within the computing device based on the operational instructions, is configured to:
• transmit, to a storage unit (SU), a data access request for an encoded data slice (EDS) associated with a data object, wherein the data access request includes a data access request identifier for the EDS associated with the data object, wherein the SU includes another memory that includes random access memory (RAM) and a hard disk drive (HDD), wherein the data access request for the EDS associated with the data object is based on at least one of:
• a check request involving the EDS associated with the data object;
• a read request involving the EDS associated with the data object;
• a write request involving the EDS associated with the data object;
• a rebuild request involving the EDS associated with the data object;
• a rebuild scanning request involving the EDS associated with the data object;
• a reallocation request involving the EDS associated with the data object;
• a rebalancing request involving the EDS associated with the data object;
• a synchronization request between mirrored vault operations involving the EDS associated with the data object;
• or
• a trimmed write request involving the EDS associated with the data object based on fewer than all of a set of encoded data slices (EDSs) generated when the data object is segmented into a plurality of data segments and a data segment of the plurality of data segments is dispersed error encoded in accordance with dispersed error encoding parameters to produce the set of EDSs;
• receive, from the SU, an empty data access response that includes no EDS based on an unfavorable comparison, as performed by the SU, of the data access request identifier with a plurality of identifiers stored within the RAM, wherein the plurality of identifiers are respectively associated with a plurality of encoded data slices (EDSs) stored within the HDD of the SU;
• and
• receive, from the SU, a data access response that includes an EDS of the plurality of EDSs having a corresponding identifier that is retrieved from the HDD of the SU based on a favorable comparison, as performed by the SU, of the data access request identifier with at least one of the plurality of identifiers.