Retention
In general, retention denotes retaining something or continue to possess something in order to use later. From the backup software perspective, retention refers to retaining the backup data in the backup storage that complies with some policies which is to avoid data redundancy in the backup server. Also the retention process should not have any impact on the backup data and it should ensure the complete and consistent data recovery during recovery process as the backup software is meant to be. The backup policies determines the retention time of data, and the limits in the aspect of backup size in the storage and the compliances that must be met to merge the data.
Vembu’s approach towards Retention
Vembu’s retention process uses data merging in order to handle the data redundancy to avoid bulk of redundant data in the backup storage. Vembu’s retention process provides options to maintain several recovery points clubbed with data merging.
There are two types of retention types available for Vembu Image Level Backups
1→ Basic Retention
2→ GFS Retention (Advanced Retention)
Basic Retention
Our basic retention process is a combination of a set of daily merge following by a synthetic merge at the end. If you configured basic retention by default daily merge will be processed for each day’s incremental and at the specified date, synthetic merge will be processed.
Vembu’s basic retention options page will be like the below one
The daily merge process takes place on the 3rd day from any specific day. For example if you configure a backup on monday with an incremental on each 4 hours, then the daily merge will takes place for these incremental on wednesday when the first incremental got successfully completed.
The synthetic merge is a process merging the daily merged data that complies to the configuration. Its upto you to decide how many daily merge data that you want to keep in the backup storage. By default, it’s configured to keep last 3 days of daily merge data and at the maximum you can keep 24 daily merge recovery points at the backup server.
Let’s say that you want to keep the last 3 days of daily merged data. You are configuring backup on 1st of Jan with an incremental on each 4 hours. Vembu VMBackup will continue to take backup at the specified intervals. On 3rd of jan, when the first incremental gets completed successfully, all the incremental on the 1st jan (excluding Full backup) will be taken for daily merge process and all incremental data will get consolidated and cumulated as a single restore point. This process continues as on 4th jan, the daily merge will be processed for 2nd jan incremental and on 5th for 3rd jan. On 6th of jan the daily merge process will occur for 4th jan’s incremental and at the completion there will be a total of 4 daily merge restore points will be available. Since our configuration is to keep last 3 daily merge restore points, the 2nd jan’s daily merge data would be synthetically merged with the 1st jan’s daily merge data and it will be a single restore point as 2nd jan. This process continues to occur to keep the last 3 daily merge data as your configuration intends.
Note: The Basic retention option will be available if you are scheduling the backup for hourly and daily manner. If you are scheduling for weekly incremental then you can only go for GFS retention.
GFS Retention(GrandFather, Father, Son)
The GFS retention process is an advanced version of retention process which has multiple phase retention phases for the backup data. The GFS retention process will have 3 phases:
1→ Daily Merge
2→ Weekly Merge
3→ Monthly Merge
All the above merges will process one after the another as per the configuration like daily merge following by a weekly merge that is followed by a monthly merge.
Vembu’s GFS retention options page will be like the below one
Like I mentioned in the basic retention, the daily merge process takes place on the 3rd day from any specific day.
The weekly and monthly merge processes will occur based on the configuration.
Let’s say that you want to have daily merge and weekly on upto every sunday and monthly upto 2nd week of wednesday, the merge process will take place as below
The Vembu VMBackup will continue to take backup according to the configuration and daily will be processed on the 3rd day for each day’s incremental upto monday morning first incremental. Once the daily merge process gets completed on monday’s first successful incremental, the weekly merge process will be triggered as the configuration is to merge weekly upto sunday. The weekly merge process will merge all the daily merge data and the incremental that were completed upto sunday 11.59 PM as a single weekly merge data. And this will be available as a weekly restore point for recovery.
Then all the incremental backup, daily and weekly merge process continue to occur until the monthly merge configuration date and time arrives that is upto 2nd week wednesday in our configuration. When the first incremental backup got successful on 2nd week’s thursday, the monthly merge process will be triggered and it will merge all the weekly merge, daily merge, and the incremental that were completed upto wednesday 11.59 PM as a monthly merge data. And this will be available as a monthly restore point for recovery.
To learn more about Vembu VMBackup and its features, visit here : Vembu VMBackup
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