What are Inodes
Definition of an inode is:
In computing, an inode is a data structure on a traditional Unix-style file system such as UFS. An inode stores basic information about a regular file, directory, or other file system object.
In other words, GNU/Linux and Unix systems uses data structures called Inodes to keep information about files (e.g. owndership, permissions...). This doesn't assume only files, but all folders, emails, anything you store on the server. If you have 1000 inodes that means that you have 1000 files in your account.
Every time when new file is added or created inode is created, too. Thus, number of inodes is actually number of your files on file system.
Many (almost all) webhosting companies do not mention inodes in their hosting plans. When you research where to host website, it is unlikelly that you'll be informed about allowed inodes distribution. However, you could be informed after you create an account on your hosting provider that number of inodes can affect the backup process. For example, Hostgator allows maximum of 250.000 inodes, but if your site reach 50.000 inodes, only databases will be included in the backup, without static files.
You may think that 50.000 is lot, but if your site(s) has builtin caching (e.g. Joomla, Wordpress with W3 Total Cache plugin...) the number will soon be reached. For example when we were developing Femina Portal, portal and forums for girls and ladies, it was hosted on our test shared account and due to sophisticated caching mechanism number of inodes were growing rapidly.
Consider that many hosting providers doesn't allow continuously publishing and deleting large numbers of files (i.e. 10,000+)
How to see current number of inodes
If you have hosting package that includes CPanel after login in left column will be displayed number of inodes with link to detail distribution overview.
How to reduce inodes number
- Download the emails contents to local PC
- Remove unwanted webfiles/data in the hosting