How It Works
Essentially, the Orlov algorithm tries to spread out "top-level" directories, on the assumption that they are unrelated to each other. Directories created in the root directory of a filesystem are considered top-level directories; Theodore Ts'o added a special inode flag that allows the system administrator to mark other directories as being top-level directories as well. If /home lives in the root filesystem (and people do set up systems that way), a simple chattr command will make the system treat it as a top-level directory.
When creating a directory which is not in a top-level directory, the Orlov algorithm tries to put it into the same cylinder group as its parent. A little more care is taken, however, to ensure that the directory's contents will also be able to fit into that cylinder group; if there are not many inodes or blocks available in the group, the directory will be placed in a different cylinder group which has more resources available. The result of all this, hopefully, is much better locality for files which are truly related to each other and likely to be accessed together.
Read more about this topic: Orlov Block Allocator
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