Unix Backup and Recovery

Chapter 19. Miscellanea

No matter how we organized this book, there would be subjects that wouldn’t fit anywhere else. This chapter covers these subjects, including such important information as backing up volatile filesystems and handling the difficulties inherent in gigabit Ethernet.

Volatile Filesystems

A volatile filesystem is one that changes heavily while it is being backed up. Backing up a very volatile filesystem could result in a number of negative side effects. The degree to which a backup will be affected is directly proportional to the volatility of the filesystem and highly dependent on the backup utility that you are using. Some files could be missing or corrupted within the backup, or the wrong versions of files may be found within the backup. The worst possible problem, of course, is that the backup itself could become corrupted, although this could happen only under the most extreme circumstances. (See Section 19.2 for details on what can happen when performing a dump backup of a volatile filesystem.)

Missing or Corrupted Files

Files that are changing during the backup do not always make it to the backup correctly. This is especially true if the filename or inode changes during the backup. The extent to which your backup is affected by this problem depends on what type of utility you’re using and how volatile the filesystem is.

For example, suppose that the utility performs the equivalent of a find command at the beginning of the backup, based solely on the names ...