SnapRAID is one of many RAID-like solutions available for disk arrays.
Some well-known alternatives include:
- unRAID - A commercial and open-source (GPL2) solution. It uses a modified Linux XFS filesystem with real-time redundancy. Integrity checksums are not natively supported.
FlexRAID- DISCONTINUED. A commercial, proprietary C++/Java application for Windows, with limited Linux support. It offered both snapshot and real-time redundancy, including integrity checksums.- ZFS - An open-source (GPL-incompatible) filesystem with real-time redundancy and integrity checksums.
- Btrfs - An open-source (GPL2) Linux filesystem with real-time redundancy. Since Linux 3.9, it supports RAID5/6 redundancy and integrity checksums. Issues have been identified, and the official wiki as of 2025 warns: "There are some implementation and design deficiencies that make it unreliable for some corner cases and the feature should not be used in production, only for evaluation or testing."
- Storage Spaces - Microsoft’s solution, integrated into Windows 8 and later. Proprietary, with real-time redundancy but no checksum support. It also has several limitations.
The primary factor for categorizing these solutions is when redundancy information is updated. In real-time solutions, parity data is updated in real-time without explicit user action, similar to standard RAID. In snapshot solutions, parity data is updated only upon explicit user request, similar to backups.
Other key factors include support for integrity checksums to detect silent data corruption and the ability to fix it, whether you can use already filled disks, whether you can recover data from non-failed disks when there are too many failures for full recovery, and whether all disks spin when reading one file.
| SnapRAID | unRAID | ZFS | Btrfs | Storage Spaces | |
|---|---|---|---|---|---|
| Redundancy model Real-time computes parity in real-time like RAID; snapshot computes parity on request, like backups. |
Snapshot | Real-time | Real-time Snapshot | Real-time Snapshot | Real-time |
| Integrity Whether data is validated with a checksum, and the default checksum type. |
Yes SpookyHash 128-bit | No [8] | Yes Fletcher4 256-bit | Yes CRC32C 32-bit | No [9] |
| Fix silent errors Whether silent errors are detected and fixed before propagating to parity. |
Yes | No [1] | Yes [3] | Yes [3] | No |
| Number of failures How many disk failures are supported? 1 for RAID5, 2 for RAID6. |
1, 2, 3, 4, 5, 6 | 1, 2 | 1, 2, 3 | 1, 2 | 1, 2 |
| More disk failures If more disks fail than the supported redundancy model, can data on non-failed disks be recovered? |
Yes | Yes | No | No | No |
| Power/Noise How many disks spin when reading a single file? |
One | One | All | All | All |
| Filled disks Can you start with already filled disks? |
Yes | Partial [4] | No | No | No |
| Add disks Can disks be added later? |
Yes | Yes | Yes | Yes | Yes |
| Operating system Which operating systems are supported? |
Linux Windows macOS OpenIndiana Solaris BSD | Linux | Linux [6] macOS OpenIndiana Solaris BSD | Linux | Windows |
| Age Year of the first official release supporting at least RAID5 redundancy. |
2011 | 2005 | 2005 | Not yet stable [11] | 2012 |
| License/Price Software license and cost. |
Open Source GPL3 Free | Open Source GPL2 $49/$109 +$36 yearly, 219$ lifetime | Open Source CDDL Free | Open Source GPL2 Free | Proprietary Included with Windows 8/10 |
| Interface Which interface is provided? GUI or command line? |
Command line Elucidate GUI, or plugin for OpenMediaVault |
Command line GUI | Command line GUI/Plugins [7] | Command line GUI [10] | GUI |
Notes
[1] - unRAID lacks native checksums and ignores silent errors. Even worse, if a parity mismatch is detected due to a silent error in the data, the parity is automatically recomputed, making it impossible to recover the silent error, even manually. Integrity checksum plugins do not help in this case, as they are not integrated into the parity-checking process. To achieve functionality similar to SnapRAID, you would need to use the Btrfs filesystem for all your data disks.
[3] - ZFS and Btrfs provide bit-rot protection comparable to SnapRAID, always verifying data before use. These three solutions represent the state of the art.
One drawback of ZFS is that its default Fletcher checksum prioritizes speed over reliability. Although it is a 256-bit checksum, Fletcher is considered weaker than alternatives. Similarly, Btrfs uses CRC32C by default, which is strong but only 32-bit. Better alternatives are "edonr" for ZFS and "xxhash" for Btrfs. In contrast, SnapRAID uses the 128-bit SpookyHash, which offers state-of-the-art checksum quality without sacrificing speed.
ZFS also employs a suboptimal RAID-Z3 algorithm that requires roughly twice the computation compared to SnapRAID’s z-parity.
[4] - unRAID supports filled disks only if they are formatted with XFS or Btrfs filesystems, but not ext4 or NTFS, the two most common filesystems for Linux and Windows.
[6] - ZFS is available on Linux at the kernel level via ZFS on Linux.
[7] - ZFS supports external GUIs, such as Napp-it, and plugins for FreeNAS and NAS4Free.
[8] - unRAID can use integrity checksums via plugins like Dynamix File Integrity, or bunker. However, these are independent of parity processing and not used to aid recovery. For example, when recovering a single failed disk with dual parity, checksums can identify additional silent errors to facilitate recovery. To achieve functionality similar to SnapRAID, you would need to use the Btrfs filesystem for all your data disks.
[9] - Storage Spaces can be used with ReFS, which supports integrity checksums, but not in Parity mode: "Although you may select Simple (no resiliency) or Parity, both options will fail the process."
[10] - Btrfs supports external GUIs, such as Rockstor.
[11] - Btrfs has supported RAID5 since 2013, but serious issues in RAID5/6 support were identified. As of 2025, these remain unresolved. The official wiki states: "There are implementation and design deficiencies that make it unreliable for some corner cases. The feature should not be used in production, only for evaluation or testing."
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