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Comment by dontlaugh

24 days ago

Which is true. It’s an old technique going back to CD games consoles, to avoid seeks.

Is it really possible to control file locations on HDD via Windows NTFS API?

  • No, not at all. But by putting every asset a level (for example) needs in the same file, you can pretty much guarantee you can read it all sequentially without additional seeks.

    That does force you to duplicate some assets a lot. It's also more important the slower your seeks are. This technique is perfect for disc media, since it has a fixed physical size (so wasting space on it is irrelevant) and slow seeks.

    • > by putting every asset a level (for example) needs in the same file, you can pretty much guarantee you can read it all sequentially

      I'd love to see it analysed. Specifically, the average number of nonseq jumps vs overall size of the level. I'm sure you could avoid jumps within megabytes. But if someone ever got closer to filling up the disk in the past, the chances of contiguous gigabytes are much lower. This paper effectively says that if you have long files, there's almost guaranteed gaps https://dfrws.org/wp-content/uploads/2021/01/2021_APAC_paper... so at that point, you may be better off preallocating the individual does where eating the cost of switching between them.

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  • Not really. But when you write a large file at once (like with an installer), you'll tend to get a good amount of sequential allocation (unless your free space is highly fragmented). If you load that large file sequentially, you benefit from drive read ahead and OS read ahead --- when the file is fragmented, the OS will issue speculative reads for the next fragment automatically and hide some of the latency.

    If you break it up into smaller files, those are likely to be allocated all over the disk; plus you'll have delays on reading because windows defender makes opening files slow. If you have a single large file that contains all resources, even if that file is mostly sequential, there will be sections that you don't need, and read ahead cache may work against you, as it will tend to read things you don't need.