hash indexed directories

I was just going through the minix filesystem when I got curious about the various filesystems out there. On reading about the features that are 开发者_运维技巧supported by ext2 I saw that hash indexed directories is one among them.

Could someone enlighten me on as to what this is?

See the link below for details on Ext2/3 Htree directory indexing:

http://ext2.sourceforge.net/2005-ols/paper-html/node3.html

Basically the filesystem uses a hash tree to store directory entries, rather than a linear list. That results in a siginificant performance improvement in directory lookup operations.