To grasp the intricacies of the retention policy, it's important to consider a few key points:
1. MSP360 employs a generation-based approach to storing backups, with each generation comprising a full and incremental backup set. The term "generation" is closely tied to your full backup frequency.
2. There are two distinct types of retention: Base retention and GFS retention. Base retention applies to backup generations, excluding the current one, which remains immune to data purging until the next generation is created.
3. GFS retention, on the other hand, is specifically applicable to full backups. It serves as a complementary retention policy that shines when you need to retain full backups for extended periods. Notably, GFS retention should surpass base retention in duration.
In your current configuration, both base retention and maximum GFS retention are set at the same value, e.g. 5 years base retention and 60 months GFS retention, resulting in backups being stored for 5 years anyway.
It's advisable to differentiate between the two:
- Set the base retention ("Keep backup for") to a duration that aligns with your need for granular restore points, typically represented by each incremental backup.
- Use GFS retention for full backups that require storage beyond the base retention period.
Let's illustrate this concept with an example. Although I don't have access to your specific backup schedule, let's assume you perform incremental backups on weekdays and full backups every Saturday. In this scenario, we'll set the base retention period to 1 month.
Base Retention:
Under this configuration, you'll have a maximum of 4 full backup generations (comprising both full and incremental backups) stored at any given time. When the 5th generation is created, the 1st generation will be purged in accordance with the base retention policy.
GFS Retention on Top of Base Retention:
Now, let's delve into how GFS retention complements base retention based on the settings in your screenshot, where weekly backups are stored for 6 weeks and monthly for 60 months.
The first full backup generated will be marked as the initial monthly and weekly backup for GFS. The 2nd, 3rd, and 4th full backups will only receive weekly tags.
When the 5th full backup initiates a new generation, incremental backups from the 1st generation will be purged in accordance with the base retention policy. However, the full backup will be retained based on the GFS retention. Additionally, the 5th full backup will again receive monthly and weekly GFS tags. The 6th and 7th full backups will be tagged as weekly backups, and so on.
Once the 7th full backup is created, the 1st full backup will lose its weekly GFS tag but won't be purged because it still has a monthly GFS tag. It will be retained in accordance with the monthly GFS retention.
Subsequently, when the 8th full backup is created, the 2nd full backup will be purged in line with the 6-month retention period for weekly backups, and this cycle continues.
I hope this explanation clarifies how retention policies work in MSP360 backups. If you have any further questions, please feel free to ask.