Retention Policies

Automatically manage backup storage by defining how long to keep backups.

Overview

Retention policies prevent unlimited storage growth by automatically deleting old backups. DBackup supports three retention modes:

Mode	Description	Best For
None	Keep all backups	Manual management
Simple	Keep last N backups	Fixed rotation
Smart (GFS)	Grandfather-Father-Son	Long-term archival

Per-Destination Retention

Retention is configured individually for each destination within a job. This means a single job can have different retention strategies per storage location.

Example

Destination	Mode	Configuration
Local NAS	Simple	Keep last 30
AWS S3	Smart (GFS)	Daily: 7, Weekly: 4, Monthly: 12
Dropbox	None	Keep all

Configuration

In the job form, expand each destination row to configure its retention:

1. Click the expand arrow on a destination
2. Select the retention mode (None / Simple / Smart)
3. Configure mode-specific settings
4. Each destination saves its retention independently

Simple Retention

Keep a fixed number of recent backups.

Configuration

Setting	Description
Keep Count	Number of backups to retain

Example

With Keep Count: 5:

• After 6th backup: 1st is deleted
• After 7th backup: 2nd is deleted
• Always maintains exactly 5 backups

Use Cases

• Development environments
• Frequent backups with short retention
• Simple rotation needs

Smart Retention (GFS)

Grandfather-Father-Son is an intelligent retention strategy that keeps:

• The most recent backups (hourly, optional)
• Recent backups (daily)
• Some older backups (weekly)
• Fewer old backups (monthly)
• Minimal very old backups (yearly)

Configuration

Setting	Description	Example
Hourly	Hourly backups to keep, off unless enabled	24
Daily	Days to keep daily backups	7
Weekly	Weeks to keep weekly backups	4
Monthly	Months to keep monthly backups	12
Yearly	Years to keep yearly backups	3

Hourly Tier

Most schedules do not need an hourly tier, so the field is hidden until you ask for it. In the policy form, click Add hourly tier below the tier inputs. It starts at 24 and can be removed again with Remove hourly tier, which sets it back to 0.

A policy that already has an hourly value opens with the field visible. Policies created before this tier existed keep exactly the same deletion behaviour, because a missing value counts as 0.

Sub-hourly schedules

A job running every 15 minutes with Hourly: 24 keeps one backup per hour and deletes the other three. That is the point of the tier, but it is a change in outcome if you are switching over from Simple retention.

How It Works

Each tier keeps the newest backup of every time bucket it covers, working from the newest backup backwards. Buckets that a finer tier already covers are skipped, and a tier only counts what it adds itself.

1. Hourly bucket: the newest backup of each of the last N hours that have backups
2. Daily bucket: the newest backup of each of the next N days
3. Weekly bucket: the newest backup of each of the next N weeks
4. Monthly bucket: the newest backup of each of the next N months
5. Yearly bucket: the newest backup of each of the next N years

The tiers add up, they do not overlap

Daily: 7 means seven days on top of what the hourly tier already covers, not seven days in total. With Hourly: 24, Daily: 7 the policy reaches back roughly nine days and keeps about 31 backups.

restic and borg read the same numbers as a union, where the daily window includes the hours the hourly tier covers. A config copied from one of those tools keeps more in DBackup than it does there.

A tier counts buckets that have backups, not wall-clock time. If a run is skipped, Hourly: 24 reaches further back than 24 hours rather than losing a slot.

Daylight saving time

Buckets are built in the timezone configured under Settings. When the clock goes back, the repeated hour maps to a single hourly bucket, so one backup loses its slot once a year. Day, week, month and year buckets are unaffected.

Example Timeline

Configuration: Daily=7, Weekly=4, Monthly=12, Yearly=2

After 1 year of daily backups:

• Daily: the 7 newest days
• Weekly: 4 further weeks, starting after the weeks the daily tier already covers
• Monthly: 12 further months, starting after the months covered so far
• Yearly: 2 further years

Total: 25 backups instead of 365, the sum of the four tiers.

Adding Hourly: 24 to the same policy keeps roughly 24 more, and the daily tier then starts after the hours it covers rather than at today.

Visual Example

Now      last 24h        7 days         weeks        months        years
 |          |              |              |             |            |
 ▼          ▼              ▼              ▼             ▼            ▼
[■■■■■■■■■■■■][■][■][■][■][■][■][■]   [■]   [■]   [■]...       [■]  [■]
 └── Hourly ──┘└───── Daily ─────┘   └ Weekly ┘  └ Monthly ┘   └ Yearly ┘

Locked Backups

Prevent specific backups from being deleted:

1. Go to Storage Explorer
2. Find the backup
3. Click Lock icon

Locked backups:

• ✅ Never deleted by retention
• ✅ Don't count against limits
• ✅ Persist indefinitely

Use Cases for Locking

• Pre-migration snapshots
• Known-good backups
• Compliance requirements
• Before major changes

Configuration Guide

Conservative (Long Retention)

Daily: 14
Weekly: 8
Monthly: 24
Yearly: 5

Keeps 51 backups over 5 years.

Moderate (Balanced)

Daily: 7
Weekly: 4
Monthly: 12
Yearly: 2

Keeps 25 backups over 2 years.

Aggressive (Minimal)

Daily: 3
Weekly: 2
Monthly: 6
Yearly: 1

Keeps 12 backups over 1 year.

Hourly Schedule

Hourly: 24
Daily: 7
Weekly: 4
Monthly: 12

Keeps 47 backups and gives a full day at hourly resolution before the daily tier takes over.

Retention Execution

Retention runs as the final step of each backup job, applied per destination:

1. Backup upload completes for a destination
2. List all backups for this job in that specific destination
3. Read each backup's metadata sidecar for its lock status, chain and creation time
4. Apply that destination's retention policy
5. Delete expired backups
6. Repeat for each remaining destination

Skipped on Failure

Retention is skipped for any destination where the upload failed. This prevents deleting old backups when the new backup didn't arrive.

Which Time a Backup Is Judged By

Backups are sorted into buckets by the creation time DBackup recorded when it wrote the backup, which is stored in the backup's .meta.json sidecar. The file's modification time on the destination is only used when there is no sidecar, for backups taken before this was recorded or for destinations DBackup cannot read files from.

This matters because a modification time is easy to lose. Copying the backup directory without preserving timestamps, moving it to another server, or restoring it from a backup of its own stamps every file with the current time. Judged by that, the entire history collapses into a single bucket and the next retention pass deletes all but one backup from it.

The run log names any backup whose two times disagree by more than an hour, so a destination in that state is visible before it costs anything.

Compliance Considerations

GDPR

• Consider data minimization principles
• Balance retention vs. "right to erasure"
• Document retention policy

SOX/Financial

• May require 7+ years retention
• Use yearly retention setting
• Lock compliance-critical backups

HIPAA

• Minimum 6 years retention
• Consider encryption for all backups
• Document access to backups

Best Practices

Match Schedule to Retention

Schedule	Recommended Retention
Hourly	Hourly: 24-48, plus Daily: 7-14
Daily	Daily: 7-14
Weekly	Weekly: 4-8
Monthly	Monthly: 12-24

Start Conservative

Begin with longer retention, then reduce:

1. Storage is cheap
2. You can't recover deleted backups
3. Analyze needs before reducing

Test Before Production

1. Create test job with short retention
2. Verify deletion works correctly
3. Then apply to production

Monitor Storage

• Watch storage growth
• Adjust retention if growing too fast
• Use compression to reduce size

Storage Calculation

Estimate storage needs:

Storage = (Backup Size) × (Retained Backups)

Example with Smart Retention (Daily=7, Weekly=4, Monthly=12, Yearly=2):

• 100MB daily backup
• ~25 backups retained
• Storage: ~2.5GB

With compression (70% reduction):

• Storage: ~750MB

Troubleshooting

Backups Not Being Deleted

1. Verify retention is enabled on job
2. Check if backups are locked
3. View job logs for retention step
4. Ensure backup ran successfully

Everything Was Deleted After Moving a Destination

Check the retention step in the run log for warnings about backups whose recorded creation time disagrees with the destination's modification time. Backups written before DBackup recorded a creation time fall back to the modification time, and a move that did not preserve timestamps puts all of them in the same bucket. Lock the backups you cannot lose before moving a destination.

Too Many Backups Deleted

1. Check retention settings
2. Verify date/time on backups
3. Lock important backups
4. Increase retention values

Wrong Backups Deleted

The GFS algorithm keeps the newest backup in each time bucket. A week with seven backups keeps the one from the end of the week, not the start.

If a destination holds more backups than the policy allows, check the retention step in the run log. Locked backups and incremental chains are both kept beyond the policy, and the log names them.

API Reference

Retention configuration in job:

{
  "retention": {
    "mode": "SMART",
    "simple": {
      "keepCount": 5
    },
    "smart": {
      "hourly": 24,
      "daily": 7,
      "weekly": 4,
      "monthly": 12,
      "yearly": 2
    }
  }
}

hourly may be omitted. A missing value counts as 0 and disables the tier.

Next Steps

• Creating Jobs - Configure backup jobs
• Storage Explorer - Browse and lock backups
• Encryption - Secure your backups