Not to be confused with H tree, a family of fractal sets.
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An HTree is a specialized tree data structure for directory indexing, similar to a B-tree. They are constant depth of either one or two levels, have a high fanout factor, use a hash of the filename, and do not require balancing.[1] The HTree algorithm is distinguished from standard B-tree methods by its treatment of hash collisions, which may overflow across multiple leaf and index blocks. HTree indexes are used in the ext3 and ext4 Linux filesystems, and were incorporated into the Linux kernel around 2.5.40.[2] HTree indexing improved the scalability of Linux ext2 based filesystems from a practical limit of a few thousand files, into the range of tens of millions of files per directory.
^Mingming Cao. "Directory indexing" (PDF). Features found in Linux 2.6.
An HTree is a specialized tree data structure for directory indexing, similar to a B-tree. They are constant depth of either one or two levels, have a...
directories and continued performance, ext4 in Linux 2.6.23 and later turns on HTree indices (a specialized version of a B-tree) by default, which allows directories...
Windows 8 (32Bit and 64Bit); it supports writing/multiple codepages, ext3 htree, journal since version 0.50 available ext2 IFS for Windows NT (Read only)...
due to the filing of several patents. Phillips had previously created the Htree directory indexing system which eventually became an official feature of...
this is inefficient, and ext3 offers a second way of storing directories (HTree) that is more efficient than just a list of filenames. The root directory...
adds the following features to ext2: A journal Online file system growth HTree indexing for larger directories Without these features, any ext3 file system...
Source: flexible inode size: > 128 bytes, up to block size dir_index: htree directory index filetype: extra file mode in dentry large_file: > 4G files...
2005 paper. ext3 Next3 List of file systems Comparison of file systems Htree Zachary Peterson and Randal Burns (May 2005). "Ext3cow: A Time-Shifting...
file systems with hash-ordered directories such as ReiserFS, ext3 (with Htree-indexes enabled) and ext4, all of which have TEA-hashed filenames. To avoid...
affect the on-disk format of the filesystem, in contrast to systems such as Htree. An in-memory of space for new entries is also maintained, allowing addition...
than 2TB. Indexed directory I (unavailable) The I attribute is used by the htree program code to indicate that a directory is being indexed using hashed...
Shardmap is a directory index design by Daniel Phillips who created the HTree and PHTree tree data structures and the Tux3 file system. A Shardmap index...
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