What is immutable storage?
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What is immutable storage?

Immutable storage is a type of storage protocol that protects stored data by preventing any changes or alterations for either a set or indefinite amount of time.

In object-oriented and functional programming, an immutable object is any object whose state cannot be modified after it is created. Similarly, immutable storage cannot be edited, deleted or rewritten once it is created and saved until a predetermined retention period ends.

Immutable storage is used to preserve records and maintain data integrity, based on the principle of write-once-read-many (WORM) data security. These types of file systems allow stored data to be accessed repeatedly once created, but not modified. 

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Understanding the value of immutable storage

Considering the increasing necessity for critical data integrity, secure data storage and reliable data backups, immutable storage presents numerous valuable advantages versus other types of file systems. 

Bolster cybersecurity

As cyberattacks become more sophisticated, traditional backup storage solutions are often insufficient. Ransomware attacks are increasingly targeting stored data directly with malware that can encrypt and lock users out of important systems (or even delete essential files entirely). Immutable backups provide a robust defense against these types of attacks by ensuring that a pristine backup is always available, thus preventing irreplaceable data loss. 

Prevent human error

Immutable storage and backup prevent data loss from various types of threats. These threats include accidental deletion to other insider threats like intentional data destruction or tampering. Even users who may have the required permissions cannot alter protected information. Whether accidental, intentional but incorrect, or specifically malicious, data that is stored as an immutable object cannot and will not be affected. 

Ensure regulatory compliance

In industries like finance or healthcare that demand strict data retention policies, immutable storage ensures that data remains untouched for the mandated period, simplifying compliance adherence. 

Types of immutable storage

Immutable storage following the write-once, read-many principles come in many forms and can be achieved through both file software and hardware solutions. In either case, organizations may elect to store their immutable data in onsite hardware. On-premises immutable storage is susceptible to local physical damage. However, on-premises immutable backups can be isolated from the broader vulnerabilities of operational filing systems. This approach still provides the many benefits associated with immutable storage. 


Cloud-based immutable storage can be easily scaled and replicated across multiple data centers, ensuring access to immutable backups even if one or more servers suffer a period of downtime. 


Air-gapping is the practice of isolating a server or other storage hardware from an organization's network. Since an air-gapped machine is not connected to the greater infrastructure, it’s insulated from any potential cyberattacks or data loss-related incidents. Air-gapped backups are generally considered to be the gold standard for data backups. 

Key features of immutable storage

These are some key features and aspects that distinguish immutable storage from other kinds of storage.

Authentication protocols

Besides, simply storing and preserving data, immutable storage can also provide strong authentication and granular permissions protocols, enabling easy access for approved persons, while effectively blocking out any unauthorized users. 

Data replication and redundancy

Immutable storage replication enables the easy creation of multiple copies. Should any issue arise, these redundancies ensure seamless business continuity and bolster data security.

Object storage dynamics

Unlike traditional file systems, object storage dynamics use a flat structure that organizes discrete units of data into objects that can be stored and retrieved more efficiently. In this way, object storage removes the complexity and scalability challenges of hierarchical file systems, improving performance and scalability. 

Customizable retention periods

Although it is possible to create immutable storage for an indefinite period of time, most data does not need to be preserved or retained forever. Immutable storage is easily customized to suit any context, allowing for flexible short- or long-term retention periods.

Benefits of immutable storage

From ransomware protection to cloud storage backups, immutable storage presents many valuable use cases.

  • Data protection: Immutable storage can provide tremendous peace of mind for companies and organizations that rely on the integrity of their data. Businesses operating in high-stakes industries—such as the law, medicine, banking, security and more—rely on immutable data storage to protect data from tampering by both outside and inside sources. 
  • Backup data security: Data backups are obviously crucial for maintaining business continuity through natural disasters, cyberattacks or any sort of system failure. Immutable backups aid in disaster recovery by creating irrefutable redundancies that can be insulated from major threats. Cloud service providers readily offer immutable data storage options housed in off-site data centers that can be easily scaled-up to service global enterprises. 
  • Compliance: Immutable cloud backup also aids in regulatory compliance by maintaining a backup copy of vital data, providing easily accessible backups in the event of any issue affecting the main file architecture. By keeping these backups in immutable storage, businesses under rigorous compliance requirements can ensure that their operations continuously satisfy data retention policies.  
Drawbacks of immutable storage

For organizations that must maintain data integrity, business continuity and sensitive internal records, the benefits of immutable security typically outweigh any drawbacks. However, since immutable storage cannot be deleted or altered before its predetermined date, large amounts of immutable data can become costly or difficult to store. 

Cloud-based immutable storage can be easily expanded depending on their providers’ pricing plans. However, whether immutable objects are stored on-premises or in the cloud, all immutable data is still susceptible to physical damage, such as fire or flooding. For this reason, cloud-based storage options are favored for their ability to replicate immutable backups across different data center locations. 

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Immutable object storage is an IBM Cloud® Object Storage feature that preserves records and maintains data integrity in a write-once-read-many (WORM), non-erasable and non-rewritable manner to protect against deletion or modification until the end of retention periods and the removal of any legal holds.

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