Reading discrete set of pages from a disk at one go

The problem is as follows:-

I have a certain file on disk which has a huge size (say a terabyte), now I want to read say N pages (discrete and not contiguous with a huge spread) from this file on disk with minimum number of disk reads (or say i want to minimize the time taken for reading these N pages from disk by minimizing the rotational and seek delays in the disk). Ideal would it be if, I start 开发者_如何学运维reading from a page and a completion of all reads occur before a rotation on disk ends. The difference in the positions of the pages is huge, so I cannot simply issue a read command starting from the first page to the last page, covering all N pages. That would take up immense amount of memory to store. (Extra - I was going though some material and bumped into "list prefetching" mechanism in a database. I read through it, and found out that such an implementation could solve my problem.)

Can somebody please help me solving this problem in the C language? Thanks in advance!

You are going to need something like Page replacement algorithm... with prefetch... You didn't tell us how will you operate with pages, how long you will need them in memory etc. But I suppose you will have to solve the situation when the memory is full and you need to release some of the pages from the memory. Look at the algorithms mentioned (LRU, MRU etc.). It is what OS's use for swapping.

You could also consider to use OS's memory mapped files - they have page replacement algorithms already implemented, but don't now about prefetch. (well depends on OS, I suppose linux will be much more advanced than windows in this topic). You can save a lot of work this way but it might not be perfetcly optimized for your case.

Regarding disk access optimizations... try to read some theory how OSes do it... Look at disk scheduling algorithms like SCAN or C-SCAN, eg. at this link.