1. A method for reducing perceived read latency, comprising: receiving a read request from a reader; issuing, via one or more processors and in response to the read request, input-output requests (IOs) to one or more storage devices; and after completion of a portion, but not all, of the IOs issued for the read request: returning a response to the reader that the read request has completed based on one or more conditions of a predefined first policy, wherein the first policy is defined based on at least one of a percentage of data corresponding to the read request available to be returned, a relative distribution of unavailable data in a scatter-gather array configured to store data associated with the read request, and an estimated time duration until full satisfaction of the read request, and unmapping unfilled pages of the scatter-gather array so that accesses to the unmapped unfilled pages generate page fault exceptions.