Although the file systems we store your data on are very robust, as there are so many users files to index and update, it is always possible that an error could occur, resulting in the need to check the filesystem and possibly repair it. Most repairs are completely successful, but they can be time consuming.
Filesystem corruption can be caused by power issues, imperfect software, and pending or actual failure of a harddrive or the device controlling it. We mirror each harddrive so that if one fails completely, the other can take over, but sometimes errors are also copied over. Fixing such problems involves checking the file index against the contents of the drive, and checking for consistency and the existence and types of data.
We encourage you to make personal backups of your website on a regular basis, or at least as often as you make major changes, as we cannot guarantee backups for you.
Note: we primarily use the Ext3 filesystem.