ok here is what I found. It came from a bsd site, but should be same same.
Code:
Each partition that has been formatted with a filesystem has three distinct areas:
an area known as the superblock
an area that contains the inode entries
the remaining area, which is used to store files
The superblock describes the parameters of the filesystem, such as the number of blocks, the size of the blocks, the size of the fragments, and the number of inodes. (If you're curious as to what else is defined in the superblock, you'll find all the parameters in man 5 fs.) These parameters were determined by the newfs command and any switches you may have passed to that command when you created the filesystem. This means that if at a later date you discover that you will run out of inodes before you run out of disk blocks, you will have to recreate the filesystem in order to change these parameters. You'll need to back up your data and test your backup first, as recreating the filesystem with the newfs utility will destroy all of the existing data on that cylinder group.
After the superblock area is the area that contains all of the inode entries. Each inode entry is 128 bytes in size and contains information about the file that it represents; this information is known as the file's "metadata." You can find out for yourself what this metadata is by reading the file /usr/include/ufs/ufs/dinode.h; even though this is a C file, it is well commented and not too hard to figure out. I've summarized its contents by listing the metadata that an inode keeps track of:
the permissions of the file
the file link count
old user and group ids
the inode number
the size of the file in bytes
the last time the file was accessed (atime)
the last time the file was modified (mtime)
the last inode change time for the file (ctime)
direct disk blocks
indirect disk blocks
status flags (chflags)
blocks actually held
file generation number
the owner of the file
the primary group of the owner of the file
it came from http://www.onlamp.com/pub/a/bsd/2001...SD_Basics.html
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