Inode table size and file system size

[taousif]

Hi all,

How can we find the maximum size of the inode table and what decides it, and how the maximum size of volume of file system is decided ?

Thanks

[Rubberman]

This depends upon the file system type you are using, though ext2/ext3/ext4/xfs/jfs are the most common Linux file system types. You need to read the technical documentation and man pages on them to get a better idea what the relationships are between inode table size, number of inodes, size of the volume, and such are.

[taousif]

Thanks Rubberman,

I want to know is there any generalized way based on which we can find out the inode limit for any filesystem?

[Rubberman]

These two options in the ext2 mkfs (from mkfs.ext2 manpage) get into it somewhat. As I said, it depends upon the filesystem type, and options available, so it isn't a cut-and-dried equation.

       -i bytes-per-inode
              Specify the bytes/inode ratio.  mke2fs creates an inode  for  every  bytes-per-inode
              bytes  of space on the disk.  The larger the bytes-per-inode ratio, the fewer inodes
              will be created.  This value generally shouldn’t be smaller than  the  blocksize  of
              the filesystem, since then too many inodes will be made.  Be warned that is not pos-
              sible to expand the number of inodes on a filesystem after  it  is  created,  so  be
              careful deciding the correct value for this parameter.

and this

       -N number-of-inodes
              overrides the default calculation of the number of inodes that  should  be  reserved
              for  the  filesystem (which is based on the number of blocks and the bytes-per-inode
              ratio).  This allows the user to specify the number of desired inodes directly.

and lastly this

       -O feature[,...]
              Create filesystem with given features (filesystem options), overriding  the  default
              filesystem options.  The default features which are enabled by default are specified
              by  the  base_features  relation,  either  in  the  [libdefaults]  section  in   the
              /etc/mke2fs.conf  configuration file, or in the subsection of the [fs_types] section
              for the filesystem type as specified by the -T option.  The filesystem type-specific
              configuration  setting  found  in  the  [fs_types]  section will override the global
              default found in [libdefaults].

              The filesystem feature set will be further edited using either the feature set spec-
              ification  specified  by  this  option,  or  if this option is not specified, by the
              default_features relation for the filesystem type being created, or in  the  [libde-
              faults] section of the configuration file.

              The  filesystem feature set is comprised of a list of features, separated by commas,
              that are to be enabled.  To disable a feature, simply prefix the feature name with a
              caret (’^’) character.  The pseudo-filesystem feature "none" will clear all filesys-
              tem features.

                   dir_index
                          Use hashed b-trees to speed up lookups in large directories.

                   filetype
                          Store file type information in directory entries.

                   has_journal
                          Create an ext3 journal (as if using the -j option).

                   journal_dev
                          Create an external ext3 journal on the given device instead of a regular
                          ext2  filesystem.   Note  that external-journal must be created with the
                          same block size as the filesystems that will be using it.

                   resize_inode
                          Reserve space so the block  group  descriptor  table  may  grow  in  the
                          future.   Useful for online resizing using resize2fs.  By default mke2fs
                          will attempt to reserve enough space so that the filesystem may grow  to
                          1024  times its initial size.  This can be changed using resize extended
                          option.

                   sparse_super
                          Create a filesystem with fewer superblock backup copies (saves space  on
                          large filesystems).

[taousif]

Thanks for man page information, I need the information at implementation level.