Announcing Long Term Retention for Azure Backup


Previously, we had announced long term retention for cloud backups from DPM. With this month’s release of the Azure Backup service, we are extending that capability to cloud backups from all currently supported SKUs of Windows Server and Windows Server Essentials.

Extending retention range in Azure backup has been a constant theme on Azure Backup feedback forum for Azure backup service. Gartner released a recent report (G00261961How to Determine If Cloud Backup Is Right for Your Servers, Published: 13 February 2014) which reported TCO of cloud backups significantly lower than tape-based back-up – “Although tape media is very inexpensive, a majority of the cost of tape-based backup is the “soft” costs, which occur around backup software, maintenance and staff time”. You might want to compute TCO for tapes similarly and consider Azure as a tape replacement for your business.

Gartner TCO comparison of Tape and cloud backup

Below is how you can use the long term retention feature in Azure back-up. We have integrated the experience in the same configuration screen that you currently use for setting short term retention policies. You need to select the weekly option that allows you to specify the schedule for a longer retention range.

Figure 1: Once every 4 weeks back up on Sundays at 9pm

Before explaining the retention range and schedule, it is important to understand how the recovery points are modeled in Azure back-up.  Each back-up is stored as a recovery point and we can currently store up to 120 recovery points which is limited to a retention range of 120 days.  Although the 120 retention point limit is still in place, we have enhanced the feature to allow a less granular option of weekly back-ups to model a longer retention period. Here is the full range of options for the maximum retention possible with this change.

Synchronize every <n> weeks Maximum retention computation Maximum retention in days
1 120x7x1 840
2 120x7x2 1680
3 120x7x3 2520
4 120x7x4 3360

Instead of using the above calculation to compute the retention range, you might wish to specify the retention range in terms of your business requirement which might be “I need a monthly back-up to be retained for 5 years”.  In this case, you can derive the number of days by multiplying with 365 (adding a correction for leap years as needed).  Here are some of the popular retention ranges we have heard from customers to illustrate the calculation. You will need to derive it similarly for your business requirement

Retention in years Retention in days Leap year correction Total Retention in days
1 365×1 +1 366
5 365×5 +2 1827
9 365×9 +3 3288

Depending on either method you used to compute the retention range, you need to then enter the value in the “Retention range in days” field and choose the appropriate synchronization frequency.  The rest of the feature works as it does currently except that you can retain your data for a much longer period.  Please click the relevant links below to get started and do send us your comments/feedback.  Thanks!