7 Best Immutable Backup Storage Solutions for Ransomware Protection in 2026

Modern ransomware doesn’t just encrypt production data — it hunts backups first. Attackers often spend days or weeks inside a network before triggering an attack, specifically targeting recovery points to maximize leverage. If backup storage sits on the same network or uses the same admin credentials as production, it’s already a target.

The answer is immutable backup storage: a layer where data, once written, can’t be modified or deleted — not by ransomware, not by a compromised admin, not by anyone — until a set retention period expires. But not all immutability is equal. Policy-based immutability can be reconfigured by an admin with the right credentials. True immutability is enforced at the hardware and OS level, so even a fully compromised environment can’t touch backup data.

This guide covers seven on-premises immutable backup solutions and what each delivers when your threat model includes a fully compromised admin account.

Four dimensions matter most:

• Immutability model — Does protection hold even against admin-level compromise? Enforced at policy level only, or also at OS/hardware level?
• Backup software compatibility — native support for Veeam, Commvault, etc.
• Operational complexity — how much Linux/storage expertise is required?
• Recovery performance — ingest and restore throughput for real workloads.

1. Object First Ootbi

Object First Ootbi — Out-of-the-Box Immutability — is a purpose-built 2U backup storage appliance designed for one purpose: ransomware-proof, immutable on-premises backup storage. It is racked, powered, and ingesting Veeam data within 15 minutes, with no Linux expertise or security configuration required.

The defining differentiator is what Object First calls Absolute Immutability — a concept the company introduced to draw a clear line between policy-based immutability and true, verifiable protection. Absolute Immutability means Zero Access to destructive actions, enforced at every layer of the stack:

• S3 buckets: S3 Object Lock in compliance mode — data cannot be modified or deleted by any account, including administrators.
• Storage application: Admin-level access is restricted; no configuration can override data immutability.
• Operating system: Root-level access is blocked entirely. Only pre-approved, vendor-controlled service procedures are permitted, with 8-eyes authorization for rare cases.
• Hardware/BIOS: Physical access is required for any firmware changes. Devices are locked by the vendor and cannot be modified remotely.

This architecture is independently verified through third-party penetration testing — a requirement Object First imposes on itself to substantiate the Absolute Immutability claim. No competing on-premises appliance publishes this level of third-party-verified immutability at every layer.

The appliance runs on a custom hardened Linux OS with S3-compatible object storage. Data is immutable from the moment it is written — no landing zone, no grace period. Veeam Backup & Replication connects natively (Veeam Ready certified for Object, Repository, SOSAPI, and IAM/STS). Deployment is a single session: rack, network, add to Veeam. The result is what Object First calls Simply Resilient — genuine security without infrastructure complexity.

Ootbi is certified against Veeam’s Zero Trust Data Resilience (ZTDR) framework, which mandates segmentation of backup software from backup storage — a principle Object First enforces by design.

• Immutability model: Absolute Immutability — S3 Object Lock (compliance), restricted admin, blocked root, hardware-locked
• Backup software: Veeam (native), Commvault, Veritas (S3-compatible)
• Form factor: 2U chassis, 18 / 36 / 72 / 144 / 216 / 432 TB per node
• Max cluster: 4 nodes — up to 1.7 PB usable
• Ingest speed: Up to 1 GB/s per node (2 GB/s for 432 TB model)
• Setup time: 15 minutes, no Linux expertise required

Best for: Veeam environments that need verified, absolute on-premises immutability without building Linux-based storage infrastructure — especially healthcare, financial services, and manufacturing environments where data must stay inside the perimeter and admin-level compromise can’t reach backups.

2. ExaGrid

ExaGrid uses an AI-powered Retention Time-Lock that keeps a non-network-accessible copy of backup data in a separate deduplication repository tier, isolated from the landing zone used for fast restores. Even with full network access to the appliance, an attacker can’t reach the protected copy during the retention period.

The tiered architecture serves two purposes: a landing zone for fast ingest and instant restores, and a repository tier for deduplication (up to 50:1) and time-locked protection. It integrates with 25+ backup applications, including Veeam, Commvault, Veritas NetBackup, Rubrik, and Oracle RMAN.

Best for: Environments with high data change rates that prioritize deduplication alongside immutability, or multi-platform backup environments needing one storage target.

3. Cloudian HyperStore

Cloudian HyperStore is software-defined, S3-compatible object storage deployable on commodity hardware. Native S3 Object Lock (governance and compliance modes) means any backup software with Object Lock support — Veeam, Commvault, Veritas — connects as an immutable target.

Clusters scale horizontally to exabyte scale at commodity hardware prices, and cloud tiering moves cold backups off-premises for long-term retention. The trade-off is complexity: deploying and maintaining a HyperStore cluster takes real storage engineering and ongoing Linux administration.

Best for: Larger organizations with dedicated storage engineering teams needing flexible, petabyte-scale on-premises object storage on commodity hardware.

4. StoneFly

StoneFly’s flagship immutable product is the DR365 VIVA — Veeam-Immutable, Veeam-Air-Gapped — combining hardware-based immutability with automated physical and network air-gapping in one unit.

DR365 VIVA enforces immutability via WORM and S3 Object Lock, blocking modification, deletion, and overwriting for admin-defined retention periods. The air-gap is policy-driven: the appliance disconnects from the network on a configurable schedule, so even a fully compromised network can’t reach it while isolated. StoneFly also offers the DR365V (hyperconverged, Veeam-ready) and DR365VS (with integrated threat detection). All are Veeam Ready certified and integrate with VMware and Hyper-V.

Best for: Organizations wanting immutability and physical air-gapping in a single appliance, without managing separate air-gap infrastructure.

5. Pure Storage

Pure Storage’s ransomware protection centers on SafeMode Snapshots, built into FlashArray and FlashBlade all-flash primary storage. No user — including root and storage admins — can modify or delete a SafeMode snapshot before its retention expires; any change to SafeMode configuration requires out-of-band verification from Pure Storage support.

Unlike the purpose-built appliances on this list, Pure Storage is primary storage first — SafeMode protects data living on the array rather than serving as a dedicated secondary backup target. It integrates with Veeam and Commvault and runs on Pure’s Evergreen subscription model.

Best for: Organizations already running FlashArray or FlashBlade that want immutable snapshot protection without adding separate backup infrastructure — not a replacement for a dedicated immutable backup target.

6. MinIO

MinIO is open-source, self-hosted S3-compatible object storage supporting S3 Object Lock in governance and compliance modes — a technically valid immutable target for Veeam or any S3-aware backup platform.

The main appeal is cost: free under AGPL, with a commercial license for enterprise support. The trade-off is operational burden — Linux administration, cluster sizing, network hardening, patching, and monitoring are all on the deploying team, with no embedded ransomware-specific hardening.

Best for: DevOps-strong teams needing a cost-effective, self-managed immutable target who have the in-house expertise to secure and maintain it.

7. Scality Artesca

Scality Artesca is a dedicated on-premises S3 “cyber vault” purpose-built for backup and ransomware recovery, available as a software appliance, hardware appliance, or an all-in-one Artesca + Veeam bundle, scaling from 20 TB to petabytes.

Artesca uses S3 Object Lock as its core immutability mechanism, backed by Scality’s CORE5 framework (immutability, encryption, access controls, monitoring, recoverability) and a $100,000 Cyber Guarantee. A built-in deployment Assistant reduces the Linux expertise normally required. It integrates with Veeam, Commvault, Rubrik, Veritas, HYCU, and Zerto.

Best for: Organizations wanting a dedicated, vendor-backed immutable object storage target with multi-vendor integration and lower operational overhead than full software-defined deployments.

How to Choose

The right choice depends on your backup software stack, in-house Linux capability, scale, and how strictly you define immutability. One rule applies everywhere: verify whether the retention lock can be overridden by an admin account before it expires. Some products market “immutability” that’s really admin-configurable WORM with override capabilities — a distinction that matters when your threat model assumes domain admin compromise.

• Veeam, zero admin overhead, absolute immutability verified at every layer: Object First Ootbi
• Deduplication alongside immutability, multiple backup platforms: ExaGrid
• Immutability + automated air-gapping in one unit: StoneFly DR365 VIVA
• Already running Pure Storage as primary storage: Pure Storage SafeMode Snapshots
• Large enterprise, storage engineering team, petabyte-scale: Cloudian HyperStore
• Dedicated immutable target with multi-vendor integration and guided setup: Scality Artesca
• Strong DevOps culture, cost is the primary constraint: MinIO (budget for operational effort)