use larger read block when moving files

[Xuefer]

benchmark shows my hd is capable of around 1MB/s  4k random seek read or(not and) write, while around 70~90MB/s sequence read or write

when defragging big files it looks like on random 4k reads a lot, HD tune monitor says 16MB/s which is better than 4k random seek but much worse than sequence read/write

 

can you please make it more sequence read for big files? and possibly take advantage of read-ahead/cache-warm-up something for small files