Because canaries tend to sing much of the time, they would stop singing prior to succumbing to the gas – therefore alerting miners to the danger. Hence, the phrase “canary in a coal mine” is frequently used to refer to a person or thing which serves as an early warning of a coming crisis.
Much like a chatty yellow bird, a business-class online backup service is actually a canary for your computer – protecting your valuable information from a variety of threats.
For example, at the completion of each backup job, Dr.Backup sends you an email message. The message provides you with the overall status of the backup such as successful, completed with exceptions, incomplete or empty.
If the subject line in your email message says “Successful” that generally means offsite backup of your data completed without a problem. An email message with a subject line containing the word “Exception” may be an early warning sign of problems.
Abnormal conditions detected are usually reported in a log file attached to the email. If you open this attachment, you may find indications of low disk space, inaccessible drives, incomplete backups, files left open, corrupt data, non-standard filenames, low system resources, incorrect file permissions and more.
Contact your local IT consultant or Dr.Backup support if you require assistance interpreting the information contained in your detailed log file.
If your computer is turned on and you don’t get a daily email message, then something else may be seriously wrong.
In other words, when the Dr.Backup canary isn’t singing…danger might be in the air !
 Wikipedia – http://en.wikipedia.org/wiki/Domestic_Canary