Retention defines the rules for retaining your backups (snapshot or recovery point) within the storage. Use the retention period to define the duration for which you want to retain your historical backups.
The objective of retention is to keep important data for future access, depending on how critical it is. Retention also ensures that backups that are no longer required are cleaned from your storage periodically, resulting in less storage utilization and costs.
Retention should consider the value of your data and the compliance requirements. The different types of data will be retained for different durations. For example, a bank's retention period for customers' financial records is different from facilities inventory records.
The main factors to consider while defining a retention period are:
- Compliance requirements
- Storage costs
- Type of data
Retention period settings
Phoenix follows the Grandfather-Father-Son (GFS) retention model wherein, in case of an overlap, the retention setting of the longer period (Son-Father-Grandfather relation) is considered. The snapshot is expired as per the settings of the higher period. For example, in case there is an overlap between the daily and weekly retention period, the weekly retention period is considered. So daily is the smallest unit and weekly overrides daily > monthly overrides weekly > yearly overrides monthly.
Also, Phoenix follows the Gregorian calendar for tracking days.
While backup schedules are configured on an hourly, daily, or weekly basis the last snapshot created by the backups on that particular day will be retained as per the retention setting.
You can define the following durations to retain snapshots.
Phoenix retains all the snapshots that are created for the number of days specified in Daily snapshots.
Phoenix considers midnight as the end of a day.
If you have configured Phoenix to back up your server multiple times within a day, Phoenix retains all the snapshots for the days specified.
|Weekly snapshots (Son)
The number of weekly snapshots that Phoenix should retain. Phoenix treats the latest snapshot in the week as the weekly snapshot.
Phoenix considers midnight on Sunday as the end of the week.
|Monthly snapshots (Father)
The number of monthly snapshots that Phoenix should retain. Phoenix treats the latest snapshot in the month as the monthly snapshot.
Phoenix considers midnight of the last day of a month as the end of the month.
|Yearly snapshots (Grandfather)
The number of yearly snapshots that Phoenix should retain. Phoenix treats the latest snapshot in the year as the yearly snapshot.
Phoenix considers the midnight of the last day of the year as the end of the year.
The snapshot name displayed on the Phoenix Management Console is snapshot creation time as per the server time zone, on which the backup occurred. Phoenix considers the time zone of the server for retaining the snapshots as per the retention setting.
Default retention period settings
If you are registering the server under default organization, Phoenix provides a default backup policy with the following retention settings:
- Daily snapshots: 14 days
- Weekly revisions: 4 weeks
- Monthly revisions: 3 months
- Yearly revisions: 3 years
The following diagram illustrates the snapshots that will be available on a given day ( Feb 9 in this example) based on the retention settings you have configured. In this example the policy is created and backups start on Dec 30 of the previous year.
On 9 Feb you will have 17 recovery points or snapshots to restore as described in the table.
Note: Daily is the smallest unit and weekly overrides daily and monthly overrides weekly and yearly overrides monthly.
Recovery points resulting from
|Daily retention setting
||You will have 11 ( 14 daily less 2 weekly less 1 monthly) recovery points (starting from 27 Jan) created due to the daily retention settings.
|Weekly retention setting
||You will have 4 recovery points for 14 Jan, 21 Jan, 28 Jan and 4 Feb created due to the weekly settings.
The weekly recovery points that coincide with the daily recovery points (28 Jan and 4 Feb) will be considered and retained as per the weekly setting. So, even though the daily retention period expires for these dates the recovery points will be retained as per the weekly settings (4 weeks).
|Monthly retention setting
||You will have 1 monthly recovery point of 31 Jan. This recovery point will be available for the next 3 months as it is a monthly retention point. So even though the 14 days daily retention period expires after 9 Feb, the recovery point will be available for the next 3 months.
|Yearly retention setting
||You will have one recovery point for 31 Dec due to the yearly retention setting. This recovery point will be available for 3 years.
Impact of retention period settings on recovery point objective (RPO)
In continuation with the example above, so let us say malware was detected on 9 Feb evening. After investigation, it was discovered that the data till 7 Feb is corrupted. In that case, the recovery point available to you will be of 6 Feb which is available due to the daily snapshot. However, there could be a data loss of data backed between 7 Feb and 9 Feb.
- Any changes that you make to the existing retention policies will be applied to all the new as well as the existing snapshots.
- Retention periods are applicable for snapshots that reside on Phoenix CloudCache and Phoenix Cloud.
- Phoenix runs a retention expiration algorithm to delete the snapshots that have crossed the expiration period. This algorithm does not delete thawed snapshots. For more information, see Snapshots.