Immutable backup storage has moved from a niche security requirement to a mainstream enterprise priority. The reason is straightforward: ransomware operators now routinely target backup repositories before triggering encryption, and standard backup storage that can be deleted with admin credentials offers no meaningful protection. Immutability — the property that backup data cannot be modified or deleted within a defined retention window, regardless of who requests it — is now the baseline requirement for serious backup security.
But not all immutable backup storage solutions implement immutability the same way. The enforcement mechanism matters enormously: software-based retention policies, S3 Object Lock compliance, network isolation, hardware-locked firmware, and vendor-authorized eradication all produce different levels of protection against different attack scenarios. Understanding these differences is what allows organizations to match the right solution to their environment.
The six platforms below cover the full spectrum of credible immutable backup storage architectures available to enterprise buyers in 2026.
1. Object First Ootbi
Object First Ootbi is a purpose-built immutable backup storage appliance designed specifically for Veeam environments. It ships as a 2U appliance with 18TB of usable capacity per node, clusterable to 1.7PB, and enforces immutability through three simultaneous, independent mechanisms: S3 Object Lock in compliance mode at the protocol layer, an OS-level root access block that prevents any software path to override retention settings, and hardware-locked firmware that cannot be modified to introduce bypass mechanisms. Together these define what Object First calls Absolute Immutability — a state in which no software action, including actions taken with full administrative credentials, can delete backup data within its retention window.
Ootbi holds the full Veeam Ready certification stack (Object, Repository, SOSAPI, IAM STS) and ZTDR (Zero Trust Data Resilience) certification, which requires verified separation between the backup application tier and the storage tier. Deployment takes approximately 15 minutes.
At the 2026 Storage Awards, Ootbi won both “Enterprise Backup Hardware Vendor of the Year” and “Ransomware Company of the Year.” “Ransomware threats continue to evolve, and organizations are increasingly prioritizing our secure, absolutely immutable backup storage as a necessary component of their cyber resilience strategy,” said Daniel Fried, SVP Worldwide Sales at Object First.
At a glance
• Three-layer Absolute Immutability: S3 Object Lock compliance + OS root block + hardware-locked firmware
• No software-accessible override path — credential compromise cannot enable backup deletion
• Full Veeam Ready stack + ZTDR certified; 15-minute setup
• Ideal for: Veeam-centric environments requiring hardware-enforced immutability with minimal operational overhead
2. Scality Artesca
Scality Artesca is a software-defined S3 object storage platform purpose-built for backup use cases. It implements S3 Object Lock in both compliance and governance modes and is designed around a cyber vault architecture — a dedicated, air-gappable immutable storage tier for backup data that is deployed independently from primary production storage.
Unlike hardware appliances, Artesca runs on commodity x86 hardware, which gives organizations flexibility to use their existing server procurement relationships while maintaining enterprise-grade immutability guarantees. It scales from a three-node edge or ROBO cluster up to data-center-scale deployments. The immutability enforcement sits at the protocol and policy layer rather than in hardware.
Artesca carries Veeam Ready Object certification and supports hybrid deployments — organizations can tier immutable backups from an on-premises Artesca cluster to cloud object storage using the same S3 protocol, with consistent immutability semantics across both tiers.
At a glance
• Software-defined on commodity x86 — no proprietary appliance required
• Cyber vault architecture: air-gappable immutable tier separate from production storage
• Scales from 3-node edge to data center; hybrid cloud tiering with consistent Object Lock semantics
• Ideal for: Organizations that want immutable S3 object storage on their own hardware without a proprietary appliance
3. ExaGrid
ExaGrid uses a tiered architecture to separate active backup data from immutable retention storage. Incoming backups land in a Landing Zone optimized for restore speed. After a configurable delay, data moves to the Retention Time-Lock tier — a network-isolated zone that becomes unreachable from the network and read-only for the duration of the retention window.
The network isolation is ExaGrid’s primary security mechanism: an attacker who compromises the backup application server cannot reach the Retention Time-Lock tier because it is not network-accessible during the lock period. This is a network-architecture approach to immutability rather than a protocol-level one, which means it provides protection even against sophisticated credential-based attacks on the backup application layer.
ExaGrid works with Veeam, Commvault, Veritas NetBackup, Dell EMC NetWorker, and other major backup applications. The built-in deduplication engine makes it particularly effective for enterprises with long retention policies where storage efficiency matters.
At a glance
• Network-isolated Retention Time-Lock tier — not reachable from network during retention window
• Application-agnostic: supports all major enterprise backup platforms
• Built-in deduplication reduces footprint for long retention policies
• Ideal for: Multi-application enterprises that need network-isolated immutability combined with deduplication savings
4. Pure Storage SafeMode Snapshots
Pure Storage SafeMode adds immutability to snapshot protection on Pure FlashArray and FlashBlade all-flash platforms. The mechanism is vendor-authorized eradication: permanently deleting a SafeMode-protected snapshot requires contacting Pure Storage support, which introduces a mandatory delay and out-of-band human verification. An attacker with full storage admin credentials still cannot delete SafeMode snapshots without Pure’s explicit authorization.
This approach is architecturally distinct from S3 Object Lock. SafeMode does not rely on a retention policy stored in the system’s software stack that an attacker might find a path to modify. The override mechanism lives entirely outside the storage system, in Pure’s support organization. This makes it highly resistant to insider threats and sophisticated external attacks that target administrative credentials.
SafeMode is a snapshot immutability layer, not a standalone backup repository. It is the most practical immutable storage addition for enterprises already running Pure primary storage, requiring no additional hardware.
At a glance
• Out-of-band vendor authorization required for snapshot deletion — cannot be bypassed with admin credentials
• No additional hardware required for Pure FlashArray or FlashBlade environments
• Consistent protection across FlashArray and FlashBlade
• Ideal for: Existing Pure Storage environments adding immutable snapshot protection without deploying separate backup hardware
5. Cloudian HyperStore
Cloudian HyperStore is an enterprise-scale S3-compatible on-premises object storage platform that implements S3 Object Lock in compliance and governance modes. In compliance mode, retention locks cannot be shortened or removed by any user — protecting backup objects from deletion even when admin credentials are compromised.
HyperStore targets petabyte-scale deployments with features tailored for large enterprise and regulated industry environments: multi-tenancy, QoS controls, erasure coding, and multi-site replication with consistent Object Lock semantics. Its compliance track record includes recognition in SEC 17a-4(f) WORM guidance, making it a natural fit for financial services and healthcare organizations where regulatory retention requirements overlap with immutable backup needs.
Deployment is software-defined on Cloudian-certified hardware or compatible commodity servers. HyperStore integrates with Veeam and most enterprise backup applications as an S3-compatible immutable repository.
At a glance
• Petabyte-scale S3 Object Lock with multi-tenancy and QoS controls
• Recognized in SEC 17a-4(f) WORM guidance — strong compliance track record
• Multi-site replication with consistent Object Lock semantics across sites
• Ideal for: Large regulated-industry enterprises that need petabyte-scale immutable object storage with a compliance track record
6. Dell PowerProtect DD (Data Domain)
Dell PowerProtect DD — the rebranded successor to Dell EMC Data Domain — is the most widely deployed purpose-built backup appliance in the enterprise market. Its immutability mechanism is DD Retention Lock, available in both compliance and governance modes. In compliance mode, locked files cannot be modified, overwritten, or deleted by any user — including storage administrators — until the retention period expires, providing WORM-level protection for backup data.
DD Retention Lock Compliance is qualified for regulatory environments including SEC 17a-4(f), HIPAA, and GDPR, with an audit trail that satisfies compliance requirements in financial services, healthcare, and government. The DD OS platform also supports immutable data management through integration with Veeam, Commvault, Veritas NetBackup, and IBM Spectrum Protect.
PowerProtect DD appliances scale from entry-level models to very large enterprise deployments and incorporate DD Boost for application-integrated backup acceleration. For organizations already standardized on Dell infrastructure, PowerProtect DD provides immutable backup storage within the existing vendor relationship and support framework — which significantly reduces procurement and operational complexity.
At a glance
• DD Retention Lock Compliance: WORM protection enforced at the appliance level, not overridable by admin credentials
• Qualified for SEC 17a-4(f), HIPAA, and GDPR compliance requirements
• The most widely deployed enterprise backup appliance — broad integration with all major backup applications
• Ideal for: Dell-standardized enterprises and regulated industries that need proven, widely supported immutable backup storage
Choosing the right storage
The six platforms here cover fundamentally different architectures. Ootbi delivers the strongest hardware-enforced immutability through three independent layers — the right choice for Veeam environments where no software override path is acceptable. Scality Artesca provides maximum hardware flexibility with software-defined S3 on commodity servers. ExaGrid combines network isolation with deduplication for multi-application enterprises. Pure Storage SafeMode is the practical answer for existing Pure environments adding snapshot immutability without new hardware. Cloudian HyperStore addresses petabyte-scale deployments in regulated industries. Dell PowerProtect DD serves enterprises already standardized on Dell infrastructure that need proven, widely supported WORM-compliant backup storage.
The common thread across all six is that immutability must be enforced at the storage layer, not just configured in the backup application. The difference between a retention policy and genuine immutability is the difference between an instruction and a physical constraint — and in a ransomware scenario, only the latter holds up when the backup application has already been compromised.
