Unraid
Unraid is a proprietary, Linux-based operating system developed by Lime Technology for creating customizable network-attached storage (NAS) systems, application servers, and virtual machine (VM) hosts using existing hardware.[1] It installs on a USB flash drive, boots into a modern Linux kernel on 64-bit x86_64 systems, and provides a user-friendly web-based graphical interface for management.[1] Unlike traditional RAID setups, Unraid employs a software-defined storage model that supports mixing drives of different sizes and interfaces (IDE, SATA, SAS), with up to two parity drives for data protection against single or dual drive failures.[1] This flexibility allows users to expand storage incrementally without replacing drives, while user-defined shares span multiple disks and optional cache drives accelerate file transfers.[1] Originating in 2005, Unraid was initially part of Lime Technology's hardware offerings but evolved into a standalone operating system focused on software innovation.[2] Founded by Tom Mortensen, the platform gained prominence through features like KVM-based virtualization and Docker container support, enabling efficient running of VMs, legacy applications, and containerized services such as media servers or backups.[3] A major milestone came in 2015 with the introduction of GPU passthrough, which expanded its appeal for gaming and media transcoding, as highlighted in community reviews.[3] By 2018, the company rebranded and hired key personnel to accelerate development, leading to enhanced security, plugin ecosystems, and ongoing updates including the Unraid 7 release in 2025 with improved array options and VM snapshots.[3] Unraid's commercial licensing model offers tiered plans based on drive count, providing lifetime access with free updates, and emphasizes ease of use for home labs, small businesses, and enthusiasts seeking control over data storage and compute resources.[4] Its parity-based protection prioritizes data integrity over performance striping, making it suitable for archival and media-heavy workloads, though it requires careful configuration for optimal speed.[1] As of 2025, Unraid continues to evolve with community-driven plugins and official apps, supporting a wide range of hardware while maintaining a boot-from-USB design that preserves data drives for storage only.[5]History and Development
Origins and Founding
Unraid was founded in 2005 by Tom Mortensen through his company, Lime Technology, as a response to the limitations of traditional RAID systems in personal media storage setups. Motivated by his own need for a reliable solution to store and back up a growing collection of DVDs and digital media, Mortensen developed Unraid to enable flexible, parity-protected storage arrays that could accommodate hard drives of varying sizes, allowing users to expand capacity incrementally without the rigidity of uniform drive requirements found in conventional RAID configurations.[2][6] The initial release of Unraid occurred on August 26, 2005, announced via a forum post on AVS Forum as a proprietary network-attached storage (NAS) operating system built on Slackware Linux. Designed specifically for home users seeking an alternative to inflexible RAID-based systems, early versions emphasized straightforward array management for data protection and sharing, prioritizing ease of use for media serving over enterprise-level complexity.[7][8] Early adoption was prominent among enthusiast communities, particularly those focused on home theater and media hoarding, where users leveraged Unraid for building large-scale backups and media libraries without the constraints of matched hardware. Initial iterations centered on core storage array functionality, enabling parity-based redundancy for personal archives, though they lacked integrated support for advanced features like virtualization, which would emerge in later developments.[7][6]Major Releases and Evolution
Unraid's development progressed significantly with the release of version 6.0 on June 14, 2015, marking a shift from its earlier iterations by introducing native Docker container support and a plugin system that expanded customization options for users.[9] This version laid the foundation for Unraid's evolution into a versatile platform for application hosting alongside storage management, after over a year of beta testing.[9] Subsequent updates in the 6.x series built on this base, with version 6.9 stable released on March 1, 2021, adding support for multiple user-defined pools formatted primarily with Btrfs for improved data organization and redundancy options beyond the traditional array.[10] Later, version 6.12.0, released on June 14, 2023, introduced ZFS filesystem support for these pools, enabling advanced features like snapshots and RAID-Z configurations on dedicated storage devices.[11] The transition to Unraid 7 began with public beta releases starting June 26, 2024, featuring an updated Linux kernel, redesigned user interface, and enhanced virtualization capabilities, while maintaining compatibility with existing setups.[12] Version 7.0.0 stable followed on January 9, 2025, incorporating native ZFS pool management directly into the core array system—eliminating the need for a traditional parity-protected array in some configurations—and bolstering networking with built-in VPN integrations and improved multi-device support.[13] The series continued with version 7.2.0 stable on October 29, 2025, upgrading to Linux kernel 6.12 LTS and OpenZFS 2.3.x, adding a fully responsive webGUI for mobile accessibility, and critical security patches.[14][15] Version 7.2.1 stable was released on November 19, 2025, providing important fixes and improvements including enhanced CPU detection, network discovery, mover schedules, and storage behavior.[16] Alongside these technical milestones, Unraid's company evolution reflected growing adoption, evidenced by active community engagement on official forums exceeding hundreds of thousands of posts by 2025. In October 2024, Unraid announced a technology partnership with Tailscale to integrate secure, zero-config VPN networking natively, with plans for deeper enhancements announced for 2025 to support enterprise-grade remote access and clustering previews.[17] This collaboration underscores Unraid's shift toward more robust, scalable features for both home and professional users.[18]Core Functionality
Storage and NAS Features
Unraid's storage system centers on a parity-protected array that enables flexible data management and fault tolerance. The array utilizes up to two parity drives to provide redundancy, with single parity safeguarding against one drive failure and dual parity protecting against two simultaneous failures.[19] This setup employs the unRAID algorithm, which stores files independently on each data drive without striping, allowing each drive to function as a self-contained unit that can be accessed or removed individually without affecting others.[19] Parity calculations occur during writes via Read/Modify/Write or Turbo Write modes, ensuring data integrity while accommodating mixed drive sizes, as long as no data drive exceeds the capacity of the smallest parity drive.[19] A key advantage of the array is its support for incremental expansion; new drives of varying sizes can be added without rebuilding the entire array, simply by starting the array after assignment, which triggers parity recalculation on the fly.[19] Higher-tier licenses permit up to 30 drives in the array, comprising 28 data drives and 2 parity drives, enabling scalable storage configurations limited primarily by hardware.[20] Data organization occurs through user-defined shares, which apply permissions at the share level to control access, export rules, and security settings across the array.[21] Complementing the array are cache pools, which introduce performance tiering by using SSDs or high-speed HDDs to accelerate read and write operations.[22] These pools act as a temporary tier for frequently accessed data, with shares configurable to use cache as primary storage and the array as secondary.[22] The built-in mover utility automates data migration, transferring files from cache to the parity-protected array on a scheduled basis to maintain protection and free up cache space.[22] Multiple cache pools can be defined, up to 35 in advanced setups, each supporting up to 60 devices for dedicated workloads.[20] Unraid facilitates NAS functionality through built-in support for standard sharing protocols, including SMB for Windows and macOS compatibility, and NFS for Unix-like systems, both configurable per share with export and security options.[23] iSCSI sharing is available via community plugins, enabling block-level access for advanced storage needs such as virtualization passthrough.Application Hosting
Unraid provides native integration with Docker, introduced in version 6.0, which allows users to deploy and manage containerized applications directly from the web-based graphical user interface (GUI). This support enables the easy installation of popular services such as media servers like Plex, cloud storage solutions like Nextcloud, and databases like MariaDB or PostgreSQL, without requiring command-line expertise. Containers are configured using pre-built templates that simplify the process by specifying repository URLs, network settings, port mappings, and environment variables, after which the system automatically pulls the image, creates the container, and starts it.[24][25] The Docker subsystem in Unraid leverages the underlying Linux kernel's containerization features, allowing multiple isolated applications to run efficiently on the same host while sharing the server's resources. Templates from the Community Applications plugin provide graphical wizards for deployment, handling details like volume mounts to map host directories—such as Unraid shares (/mnt/user/appdata)—to container paths for persistent data storage. This persistent volume mapping ensures that application data survives container restarts or updates, integrating seamlessly with Unraid's array-based storage system.[25][26] In addition to Docker, Unraid features a plugin system for extending core operating system functionality, with installations managed through a central repository via the Community Applications interface. These plugins, maintained by the community, include tools for system monitoring (e.g., Dynamix System Statistics), automated backups (e.g., CA Backup / Restore Appdata), and security enhancements (e.g., Unassigned Devices for mounting external drives), with over 2,000 options available in total across plugins and Docker templates. Plugins are installed similarly to containers, using one-click deployment from the catalog, and they operate as lightweight extensions without the full isolation of containers.[26][27] Resource allocation for hosted applications is configurable to optimize performance, particularly for resource-intensive tasks. Users can implement CPU pinning by adding Docker extra parameters like --cpuset-cpus="2,3" in the container's advanced settings, reserving specific cores for an application to prevent contention with the host OS or other services. GPU passthrough to containers is supported for hardware acceleration, such as NVIDIA transcoding in Plex, by installing the NVIDIA Container Toolkit plugin and specifying --runtime=nvidia or --gpus all in the template, allowing direct access to the GPU without dedicating it exclusively to a virtual machine. These features enable fine-tuned resource management while maintaining the flexibility of Unraid's shared storage model.[28]Virtualization Support
Unraid introduced KVM-based virtualization with the release of version 6.0 in 2015, transitioning from the earlier Xen hypervisor to provide a more modern and performant foundation for hosting virtual machines (VMs). This implementation leverages KVM as the type-1 hypervisor and QEMU for device emulation, managed through Libvirt for XML-based VM configurations, enabling the execution of full guest operating systems alongside the host's storage and application services.[29][30] The system supports a variety of guest operating systems, including Windows, Linux distributions, and macOS, allowing users to run diverse workloads such as desktop environments, servers, or specialized applications. Hardware passthrough capabilities extend to PCI devices, GPUs, and USB controllers via VFIO and IOMMU groups, facilitating near-native performance for demanding tasks like gaming, video editing, or AI model training by dedicating host resources directly to the VM. For remote management, Unraid provides built-in VNC access with optional password protection, while SPICE protocol support offers enhanced graphics and input handling for improved user experience, particularly in Linux guests. Additionally, VM snapshotting is available for QCOW2-formatted disks, enabling point-in-time state captures and rollbacks to aid in testing, backups, or recovery scenarios.[30][31][32] VM disk images integrate seamlessly with Unraid's storage pools, typically stored in the dedicateddomains share on cache drives or the parity-protected array for redundancy, supporting both RAW format for optimal I/O performance and QCOW2 for features like snapshots and copy-on-write efficiency. Starting with version 7.0 in 2025, enhancements include a "migratable VM" configuration option, which prepares guests for live migration across compatible hosts in preview functionality, further expanding Unraid's utility as a flexible virtualization platform.[31][33][34]