If I have 3 million pages, which directory structure is better?
Method 1. ~/123456789.htm
(Putting all the 3 million pages into the same folder without any sub folders)
Method 2. ~/789/123456789.htm
(Create 999 sub-folders, each sub-folder contains about 3000 pages)
For Windows Server 2008, which folder structure is faster? (For file creation, reading and deletion)
IMO putting thousand of files in one directory isn't a good practice.
One option is to get the hex representation of the integer,
eg 123456789 -> 075BCD15
and use this directory structure: ~/07/5B/CD/15.htm
I think it depends highly on your filesystem format (NTFS? ext3?) since you haven't specified you want to list files, I think 3 million is fine for a single directory to create/read/delete files.
From experience, I can say it is not fun to use NTFS to list a folder with even 30,000 files.
It is definitely faster to got with the subfolder variant. Our DMS stores files based on their creation date in a structur like ./YYYY/MM/DD/HH/MM/, which is a good was to look up a file if you know its age.
Just imagine that NTFS on Windows 2008 has directories implemented as a list. If you have 3.000.000 files, the whole list is to be searched. If you have a tree, with maybe 10 entries per level (You need a deepness of 6 then, because you have 3*10^6 files), access to individual files is much faster.
If you always want to access all files at once, e.g. for batch processing, the all files in one folder strategy might be the fastest, but then don't accidentially click on that folder in Explorer, except you need a reason to get you some coffee :)