Administrators using Acronis Cyber Protect Cloud often notice that cloud storage space remains occupied even after backups are deleted. This behavior is intentional and is usually caused by immutable backup retention, a security feature designed to protect data from ransomware, accidental deletion, and insider threats.
This article explains why deleted backups still consume space, how immutability works at a technical level, and what actions administrators can and cannot take to reclaim storage safely and correctly.
Immutable Backups (WORM Storage)
Prevents modification or deletion of backups for a defined period
Soft Delete Mechanism
Deleted backups are hidden but not physically erased immediately
Retention Policies
Controls how long backups are stored
Encrypted Storage
AES-256 encryption for all backup data
Ransomware Protection
Ensures compliance with cyber-resilience best practices
When a backup is deleted from the console:
Catalog metadata is removed
Backup blocks remain stored if immutability is active
Storage is released only after the immutability lock expires
From your backup details:
deleted_immutable = true
immutable_size > 0
marked_for_deletion = false
This means:
The backup is logically deleted
The data blocks are cryptographically locked
Permanent deletion is not allowed yet
data_size = 0 but Storage Is Still Used| Field | Meaning |
|---|---|
| data_size = 0 | No active recovery points |
| immutable_size > 0 | Locked backup blocks still stored |
| deleted = false | Not eligible for physical deletion |
| marked_for_deletion = false | Awaiting immutability expiry |
Analogy:
Index removed, warehouse sealed.
Cleaning old ERP or Tally backups
Reducing cloud storage billing
Removing decommissioned servers
Investigating “storage not freeing” complaints
Auditing backup retention policies
Go to Backup Storage → Locations
Disable Hide deleted
Select the deleted backup
Open Details
Look for:
Navigate to:
Note:
Immutability duration (days)
Applies per backup creation date
Formula
Until this date:
❌ “Delete permanently” will not appear
❌ Storage cannot be freed manually
| Action | Result |
|---|---|
| Force delete via UI | ❌ Not allowed |
| API deletion | ❌ Blocked |
| Acronis support override | ❌ Impossible |
| Removing agent | ❌ No effect |
| Deleting tenant | ❌ No effect |
This complies with WORM (Write Once Read Many) standards.
Immutability protects against:
Ransomware encryption
Malicious admin actions
Accidental deletions
Even global administrators cannot bypass the lock
Required for many cyber-insurance and compliance frameworks
⚠️ Disabling immutability weakens ransomware protection.
| Setting | Recommended |
|---|---|
| Daily backups | Retain 7–14 days |
| Monthly backups | Retain 1–2 copies |
| Immutability | 7–14 days |
| Full backups | Avoid frequent fulls |
| Old plans | Disable permanently |
Never re-enable old backup plans
Review storage usage monthly
Align retention with business RPO/RTO
Document immutability policy for clients
Cause: Immutability still active
Fix: Wait until immutability expires
Cause: Backup is immutable
Fix: Not possible until lock expiry
Cause: Misunderstanding of soft delete
Fix: Explain immutability lifecycle
“Your backup is deleted but protected by anti-ransomware lock.
It will auto-remove once the protection period ends.
This ensures no one—not even admins—can erase it early.”
Deleted backups in Acronis Cyber Protect Cloud do not immediately free storage when immutability is enabled. This is expected, secure, and irreversible by design. Storage space is released automatically after the immutability retention period expires, ensuring maximum protection against ransomware and accidental data loss.
Administrators should focus on correct retention planning, not forced deletion, to optimize storage usage while maintaining security.
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