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Allocation algorithms

Here are the allocation algorithms that ext2 file system managers must use. We are adamant on this point. Nowadays, many users use more than one operating system on the same computer. If more than one operating system use the same ext2 partition, they have to use the same allocation algorithms. If they do otherwise, what will happen is that one file system manager will undo the work of the other file system manager. It is useless to have a manager that uses highly efficient allocation algorithms if the other one does not bother with allocation and uses quick and dirty algorithms.

Here are the rules used to allocate new inodes:

• the inode for a new file is allocated in the same group of the inode of its parent directory.

• inodes are allocated equally between groups.

Here are the rules used to allocate new blocks:

• a new block is allocated in the same group as its inode.

• allocate consecutive sequences of blocks.

Of course, it may be sometimes impossible to abide by those rules. In this case, the manager may allocate the block or inode anywhere.

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