How do I allocate contiguous disk space?

Question

I am developing a system which works with lots of files and doing some google searches I read about improving the speed of information retrieval by the hard disk. But since I work with Java, I can't find any library to work with this issue. I have a very vague knowledge in C++, and found something about hard disk information retrieval with IOCTL. Apparently there is no way of getting specific information like how many contiguous free blocks can I get from my hard disk or the maximum of contiguous free blocks it have. I am currently working with Windows 7 and XP. I am aware of the use of JNI but I have strong problems with C++. But even searching for C++ solutions I can't find anything. Maybe I am doing some wrong queries on Google. Could someone please give me a link, suggestions of study or anything? I am willing to study C++ (although I have almost no free time).

Thank you very much!

PS-Edit: I know it would practically make no difference. But I really need to learn about this. But thanks to everyone giving advices.

Answer 1

AFAIK there's no built in way nor a 100% pure java solution. The problem is that retrieving that kind of information depends on the platform and since Java should be platform independent you only can use a common subset.

Answer 2

Have you identified a performance problem? If not, then don't do anything.

Are you sure that the physical distribution of the files on the disk is the cause of this performance problem? If not, then measure where the time is spent in your application, and try to improve the algorithms, introduce caches if necessary.

If you have done all this, and are sure it's the physical distribution of the files on the disk that's causing the performance problem, have you thought about buying a faster disk, or about using several ones? Hardware is often much cheaper than development time.

I very much doubt the physical distribution of the files on the disk has a significant impact on the performance of your app. I would search elsewhere first.

Answer 3

Captain Kernel explains here that this won't necessarily increase disk performance, and beyond that, is not possible without extensive work.

Answer 4

NTFS already tries to allocate your files contiguously, as stated in this blog post of a Windows 7 engineer. Your files will only be fragmented if there is no big enough contiguous chunk of free space.

If you believe that it is important for your files not to be fragmented, then I think the best option is to schedule a nightly defragmentation of your disk. That's more of a system administration problem.

Finally, fragmentation is irrelevant on SSD disks.