A problem of latency during a read of a file is solved by activating multiple concurrent read threads and also by prefetching blocks of file data from storage to a file system cache. Prefetching ensures that by the time that a client or application needs more file data, the file data will already have been read from storage and written to the cache as a background operation. For example, a file server responds to a request to read an extent of file data consisting of eight consecutive file blocks by activating concurrent block read threads for reading the file blocks and by prefetching from the storage to the cache eight more consecutive blocks of data from the file.