Unraid is a proprietary operating system that stores complete files on individual disks; it doesn’t stripe them, as is typical with RAID arrays (hence the “un”). As a result, recovering data from an Unraid setup is generally more straightforward than traditional RAID recovery.
If your hardware fails or the operating system becomes corrupted, you can typically just remove the drives, connect them to a different computer, and access the files directly.
Of course, data loss can still occur; as with a standard RAID, Unraid is not a substitute for backup. Below, we’ll explore the architecture of Unraid and explain a few of the challenges that data recovery engineers face when handling these systems.
If you’ve lost access to data, we’re here to help. Datarecovery.com provides risk-free standard evaluations for all multi-drive systems (including Unraid), and with our no data, no charge guarantee, you only pay if we recover the files you need.
Get started by setting up a ticket online or call 1-800-237-4200 to speak with an expert.
Unraid Data Recovery: How Unraid Stores Data
Traditional RAID configurations use data striping. In a striped array, a single file is broken into blocks and written across multiple hard drives. That allows for faster access speeds and a degree of redundancy, both of which are useful for server setups.
Unraid is designed for home servers, so it operates differently — it functions more like a JBOD (Just a Bunch Of Disks) with an optional layer of parity for redundancy. In this context, redundancy means that one physical device can fail without causing permanent data loss.
In Unraid, files are stored whole on individual disks. Unraid presents these disks as a single unified share (or volume to the user), but each disk has file integrity. Since Unraid does not stripe data, the drives can be mounted individually outside of the Unraid server, provided that you have a machine that can read them.
Unraid typically formats data drives using XFS, Btrfs, or occasionally ReiserFS (on older builds). Note that windows and macOS do not natively support these Linux-based filesystems, so if you’re trying to read an Unraid drive on a Windows system, you’ll need additional software. There’s a whole unraid subreddit with plenty of threads on this subject — if you’re new to unraid, start there.
Handling Parity Drive Failures
Unraid provides fault tolerance through a dedicated parity drive (or two, in dual-parity setups). The parity drive does not contain any readable files. It’s just a set of binary calculations that allow the system to rebuild a failed data drive.
If a single data drive fails physically, the Unraid OS uses the parity drive and the remaining data drives to emulate the missing data. You can replace the failed drive, and Unraid will reconstruct the data onto the new disk.
However, that parity is limited — that’s why we’re constantly telling clients that parity is not backup. If you lose more data drives than you have parity drives (for example, two data drives fail in a single-parity setup), the data on the failed drives is lost.
The good news is that because there is no striping, the data on the surviving drives remains intact and accessible. You only lose the data specifically located on the failed hardware.
Unraid Data Recovery: Steps to Take
If you cannot access your Unraid server, follow these steps:
- Stop Writing Data: Continued use of a failing array can overwrite valid data or cause further physical damage to struggling mechanical drives.
- Identify the Failure: Determine if the problem is the USB boot device (common with Unraid), the controller card, or the hard drives themselves.
- Attempt Linux Mounting: Connect the working drives to a Linux environment to verify that the files are accessible.
- Check Documentation: Refer to the official Unraid manual for specific commands regarding drive replacement and parity sync if you are attempting to rebuild the array in place.
Professional Solutions for Unraid Data Recovery
While Unraid’s architecture allows for easier DIY recovery in logical failure scenarios, physical hardware failure can push the system past its parity and cause permanent data loss. If a drive is clicking, beeping, or failing to spin up, software tools cannot recover the data.
Datarecovery.com utilizes certified cleanrooms to safely repair physically damaged hard drives. All of our locations feature fully outfitted laboratories, and our industry leading hardware inventory allows for fast turnaround times and flexible pricing.
Our engineers specialize in piecing together fragmented filesystems — even when the partition tables are damaged or when an Unraid rebuild has failed halfway through. We operate on a no data, no charge guarantee, and all standard cases start with a risk-free evaluation.
Contact our team at 1-800-237-4200 for a free evaluation or submit a case online to get started.
