When all the inodes are consumed then even though you have free space, you will get the error that filesystem is full. So, to check whether there is space available, we have to use the command df –i.
Sometimes, it may happen file system or storage unit contains the substantial number of small files, and each of the files takes 128 bytes of the inode structure then inode structure fills up, and we will not be able to copy any more file to the disk. So, to rectify the problem, you need to free the space in inode storage, and you will be able to save more files.