Another advantage of indexed allocation is
that the locations of all the blocks in the file can be determined from the directory entry, so random access
is possible. A disadvantage is that any corruption of the directory entry can make it impossible to recover the
information in the file.
In UNIX a file directory entry is called an i-node or inode, for index-node. Among other things, the inode
contains pointers to the file blocks, permissions, ownership information, and times of last access and modification.
Since directories are just files in UNIX, each directory has an inode, too. When a program opens a file like
/usr/work.txt, the system locates the inode for the root directory (almost always set to inode 2), and then reads
the blocks of the root directory looking for something called ???usr.??? When it finds ???usr,??? it will also find the inode
for ???usr.??? Then it can read the file that is the directory ???usr??? and look for something called ???work.txt.??? When it
finds ???work.txt,??? it will also find the inode for ???work.txt.??? From the inode of ???work.txt??? the system will find
pointers to all the blocks of the file.
Journaling File Systems
Some newer file systems incorporate logging or journaling of file system transactions.
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