This article focuses specifically on the storage layer: on-premises platforms that accept backup data and enforce immutability independently of the backup application. These are not backup applications — they are the targets where backup applications write data, and where immutability must be enforced even if the backup application server is compromised.

The six solutions below cover the full spectrum of on-premises immutable backup storage architectures available to enterprise buyers in 2026.

1. Object First Ootbi

Object First Ootbi is the only purpose-built immutable backup storage appliance designed exclusively for Veeam environments. It ships as a 2U appliance with 18TB of usable capacity per node, scalable to 1.7PB in a cluster, and enforces immutability through three independent layers: S3 Object Lock in compliance mode at the protocol level, an operating system configured to block root-level access via any software path, and hardware-locked firmware that cannot be modified to introduce an override mechanism. Object First calls this combination Absolute Immutability.

The three-layer architecture means that compromising one enforcement mechanism does not expose the others. An attacker with full storage admin credentials cannot delete backup data within its retention window — there is no software path to override the hardware-enforced protection. Ootbi holds the complete Veeam Ready certification stack (Object, Repository, SOSAPI, IAM STS) and ZTDR certification, which requires verified separation between the backup application tier and the storage tier. Setup 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.

Why it qualifies

  • Absolute Immutability: three independent enforcement layers with no software override path
  • Full Veeam Ready certification stack + ZTDR certified
  • 2026 Storage Awards: Enterprise Backup Hardware Vendor of the Year + Ransomware Company of the Year

Best for: Veeam-centric environments that need the strongest hardware-enforced immutability with minimal operational overhead

2. ExaGrid

ExaGrid protects backup data through a two-tier architecture. Incoming backups land in a Landing Zone optimized for restore speed. After a configurable delay, data moves to the Retention Time-Lock tier, which becomes network-isolated and read-only for the duration of the retention window. An attacker who compromises the backup application server and storage admin credentials still cannot reach the Retention Time-Lock tier — because it is not reachable from the network during the lock period.

This network-isolation approach to immutability is architecturally distinct from S3 Object Lock: there is no protocol-level retention policy to attack, only a network boundary that closes after each backup job. ExaGrid integrates with all major backup applications — Veeam, Commvault, Veritas NetBackup, Dell EMC NetWorker, and IBM Spectrum Protect — and includes built-in deduplication that provides meaningful storage efficiency for long-retention policies.

Why it qualifies

  • Network-isolated Retention Time-Lock tier: unreachable from the network during lock window
  • Application-agnostic: compatible with all major enterprise backup platforms
  • Built-in deduplication reduces storage footprint at long retention periods

Best for: Multi-application enterprise environments that need network-isolated immutability with deduplication savings

3. Scality Artesca

Scality Artesca is a software-defined S3 object storage platform built specifically for backup use cases. It implements S3 Object Lock in compliance and governance modes and is designed around a cyber vault architecture: a dedicated, air-gappable immutable storage tier deployed separately from primary production storage. Because it runs on commodity x86 hardware, organizations are not locked into proprietary appliance procurement — capacity scales by adding standard servers.

Artesca scales from a three-node edge or ROBO cluster up to data-center-scale repositories. It carries Veeam Ready Object certification and supports hybrid configurations where immutable backups tier from an on-premises Artesca cluster to cloud object storage with consistent S3 Object Lock semantics preserved across both tiers. The software-defined model places immutability enforcement at the protocol and policy layer.

Why it qualifies

  • Software-defined on commodity hardware: 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

Best for: Organizations that want enterprise-grade immutable S3 object storage on their own hardware without appliance lock-in

4. NetApp SnapLock

NetApp SnapLock is the WORM and compliance feature set built into NetApp ONTAP, running across AFF all-flash, FAS hybrid, and StorageGRID object storage platforms. SnapLock Compliance mode creates volumes where files become truly WORM-protected once committed: they cannot be deleted or modified by any user — including the storage administrator — until the retention period expires. The retention clock cannot be shortened, and compliance volumes cannot be destroyed until all WORM data has expired.

SnapLock has a two-decade compliance deployment history and is certified for SEC 17a-4(f), FINRA, MiFID II, and CFTC requirements, making it relevant for regulated industries where compliance archiving and backup protection requirements overlap. It integrates with NetApp SnapVault for immutable backup copies and with Veeam as an ONTAP NAS immutable repository. For organizations already running ONTAP infrastructure, SnapLock is typically the lowest-friction path to compliant immutable backup storage.

Why it qualifies

  • Compliance mode: no admin override, retention cannot be shortened, volumes cannot be destroyed until all WORM data expires
  • Certified for SEC 17a-4(f), FINRA, MiFID II, CFTC — two decades of regulatory deployment
  • Runs natively on AFF, FAS, and StorageGRID — no additional hardware for existing NetApp environments

Best for: Regulated enterprises in financial services, healthcare, and government already running NetApp ONTAP

5. Dell PowerProtect DD (Data Domain)

Dell PowerProtect DD — the successor to Data Domain — is the most widely deployed purpose-built backup appliance in enterprise. Its immutability mechanism is DD Retention Lock, available in Compliance and Governance modes. In Compliance mode, locked files cannot be modified, overwritten, renamed, or deleted by any user, including storage administrators, until the retention period expires. The period cannot be shortened after a file is locked.

DD Retention Lock Compliance is qualified for SEC 17a-4(f), HIPAA, and GDPR. DD Boost integration with Veeam, Commvault, Veritas NetBackup, and IBM Spectrum Protect gives PowerProtect DD broad ecosystem coverage. The appliance line scales from entry-level to multi-petabyte deployments and includes DD Boost for hardware-accelerated deduplication. For Dell-standardized environments, PowerProtect DD consolidates immutable backup storage within the existing vendor relationship and support framework.

Why it qualifies

  • DD Retention Lock Compliance: no admin override, retention cannot be shortened after locking
  • Qualified for SEC 17a-4(f), HIPAA, GDPR compliance requirements
  • Most widely deployed enterprise backup appliance — broad integration across all major backup applications

Best for: Dell-standardized enterprises and regulated industries needing proven, broadly supported immutable backup storage

6. Cloudian HyperStore

Cloudian HyperStore is an enterprise S3-compatible 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 — including the storage administrator. HyperStore is designed for petabyte-scale deployments and includes enterprise operational features that are rare in this category: multi-tenancy with tenant-level isolation, QoS controls, erasure coding across sites, and multi-site replication with Object Lock semantics preserved across all sites.

HyperStore carries a compliance track record recognized in SEC 17a-4(f) WORM guidance, making it relevant for financial services and healthcare enterprises where regulatory retention requirements overlap with backup security 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.

Why it qualifies

  • S3 Object Lock compliance mode: no admin override at any scale up to petabytes
  • Multi-tenancy, QoS, erasure coding, and multi-site replication with consistent Object Lock semantics
  • Recognized in SEC 17a-4(f) WORM guidance — relevant for both backup security and regulatory archiving

Best for: Large enterprises and regulated industries that need petabyte-scale immutable object storage with a compliance track record

Choosing the right storage

The six platforms here address different organizational profiles. Ootbi is the answer for Veeam-centric environments where hardware-enforced immutability with no software override path is the priority — its three-layer Absolute Immutability sets the benchmark in the purpose-built appliance category. ExaGrid fits multi-application environments where network isolation and deduplication savings are the primary requirements. Scality Artesca gives organizations maximum flexibility to build immutable S3 object storage on their own hardware selection without proprietary lock-in. NetApp SnapLock is the natural choice for ONTAP-standardized environments and regulated industries with deep compliance certification requirements. Dell PowerProtect DD serves Dell-standardized enterprises with its broad ecosystem integration and proven compliance qualifications. Cloudian HyperStore addresses the largest-scale deployments where petabyte-range immutable object storage with multi-tenancy is required.

The common requirement across all six: the storage layer must enforce immutability independently of the backup application. If an attacker can compromise the backup server and use those credentials to delete backup data, the storage is not providing genuine immutability — regardless of what the vendor marketing says.