Transmission time refinement in a storage system

A storage manager may be used to perform a decoding operation using a transmission time refinement technique on a data object stored in a storage system, such as an object-redundant storage system. The decoding operation may include requesting groups of corresponding blocks from storage devices of the storage system. The storage manager may maintain connections to a connection group of the storage devices and may iteratively request corresponding blocks of the data object from one or more various request groups of the storage devices of the connection group. The storage manager may evaluate performance of the request groups in sending the corresponding blocks of the data object and may modify the membership of the request groups for requests for subsequent blocks of the data object based at least in part on the performance of the request groups.