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Barracuda Backup

How does the Barracuda Backup Service weekly retention policy work?

  • Type: Knowledgebase
  • Date changed: 4 years ago
Solution #000003878

Scope:

All Barracuda Backup Servers, all firmware versions.

Answer:
Retention Policies tell the Barracuda Backup Server what data to retain and how long to retain it. The way that weekly retention time periods are dealt with and represented within retention policies is described below:

 

Problem

The logic used in weekly retention time periods is somewhat confusing. To understand how weekly time periods work and why they require clarification, it is important to grasp the problem that arises from using them. Weeks are problematic from a programming sense.  While days always fit neatly into months and months always fit neatly into years, weeks can span across the end of months and the end of a year.

 

For the purpose of this illustration we will assume that a calendar week always begins on a Sunday at midnight and ends on Saturday night at 11:59:59 PM. We will also assume that during your retention policy you want to keep only the latest file revision for each week and only the latest file revision of each month. When using a calendar week, your actual latest file revision of the month will be purged by your weekly retention policy for any month that does not end on a Saturday. When your monthly retention policy kicks in, it will no longer have the latest revision of the month available, since it was purged by the preceding weekly policy. Instead, the latest revision available will be the last Saturday in the month.

 

Since weeks often span the calendar year boundary of December 31st, the same problem would occur if a weekly retention setting were applied before a yearly retention setting in the policy. Being able to keep the actual latest revision of months and years is an important functionality of a good data retention system. Therefore, Barracuda has introduced the following concept of weekly purging in order not to break the more important monthly and yearly schedules.

 

Solution

Instead of Sunday through Saturday, weeks are considered periods of 7 days in a row beginning on the first of each month. According to the purge schedule the last "week" of the month may be 3, 2, 1 or actually 7 days long depending on the number of days (31, 30, 29, or 28 respectively) in the month.

 

Therefore, under a weekly retention setting, the retention policy will keep the latest revision of the file for the greatest day in the week. For the first four 7 day periods, it will always keep the file revision from the 7th, 14th, 21st, and 28th day of the month. For months longer than 28 days, it will end up keeping the last day of the remaining week, which will always be the last day of the month. That way, when the subsequent monthly or yearly retention schedule is applied, it will always have the latest revision of the month or year available for retention.
 

Link to This Page: 

https://campus.barracuda.com/solution/50160000000HXlAAAW