+A directory with the 'T' attribute will be deemed to be the top of
+directory hierarchies for the purposes of the Orlov block allocator.
+This is a hint to the block allocator used by ext3 and ext4 that the
+subdirectories under this directory are not related, and thus should be
+spread apart for allocation purposes. For example it is a very good
+idea to set the 'T' attribute on the /home directory, so that /home/john
+and /home/mary are placed into separate block groups. For directories
+where this attribute is not set, the Orlov block allocator will try to
+group subdirectories closer together where possible.
+.PP
+A file with the 't' attribute will not have a partial block fragment at
+the end of the file merged with other files (for those filesystems which
+support tail-merging). This is necessary for applications such as LILO
+which read the filesystem directly, and which don't understand tail-merged
+files. Note: As of this writing, the ext2 or ext3 filesystems do not
+(yet, except in very experimental patches) support tail-merging.
+.PP
+When a file with the `u' attribute set is deleted, its contents are
+saved. This allows the user to ask for its undeletion. Note: please
+make sure to read the bugs and limitations section at the end of this
+document.
+.PP
+The 'X' attribute is used by the experimental compression patches to
+indicate that a raw contents of a compressed file can be accessed
+directly. It currently may not be set or reset using
+.BR chattr (1),
+although it can be displayed by
+.BR lsattr (1).
+.PP
+The 'Z' attribute is used by the experimental compression patches to
+indicate a compressed file is dirty. It may not be set or reset using
+.BR chattr (1),
+although it can be displayed by
+.BR lsattr (1).