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RAID helps a NAS keep working through some disk failures; snapshots let you roll back files or folders to an earlier state; and backups give you a separate copy to recover if the NAS or its storage is lost. They solve different problems. RAID is not a backup, and a snapshot kept only on the affected NAS may not survive the event you need to recover from.
What RAID, snapshots, and backups protect against
| Method | What it does | Useful for | Key limitation |
|---|---|---|---|
| RAID | Provides redundancy within a storage group, depending on the RAID level and configuration. | Keeping the NAS or service available through some member-disk failures. | It is not an independent copy. It does not cover every hardware failure, accidental deletion, corruption, theft, fire, or compromise. Synology warns that RAID crashes and hard-drive failures can still cause data loss (Synology, updated May 8, 2026). |
| Snapshot | Records a storage unit or shared folder at a point in time. | Restoring an earlier state or prior file or folder version after a modification or deletion, as QNAP describes in its QTS Storage & Snapshots Quick Start Guide. | A snapshot stored only on the affected NAS or pool shares its failure domain. Support varies by model, filesystem, and software. |
| Snapshot replication | Copies snapshots to another storage pool or NAS. | Keeping snapshot recovery points at a separate destination. QNAP documents local-pool and remote-NAS replication in its QTS 5.0.x User Guide. | Replication to another pool in the same NAS still shares the NAS. Remote replication depends on the destination, security, and retention settings; features and protection claims vary by product and version. |
| Backup | Creates a recoverable copy at a separate destination. | Recovering data after loss or failure of the source NAS. Destinations can include an external USB device, another NAS, or cloud storage; see Synology’s backup guidance and QNAP’s QuTS hero 5.0.x backup guide. | It must be configured and monitored. Synchronization alone may copy unwanted changes or deletions rather than preserve a usable recovery point. |
How the recovery copies differ
RAID: redundancy for some disk failures
RAID operates within a storage group. Depending on the selected level and configuration, it can provide tolerance for certain member-disk failures and help maintain availability. It does not make an independent copy of the data: a deletion, corruption, or incident affecting the NAS can affect the data even when the disks are arranged redundantly.
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Snapshots: convenient points to roll back to
A snapshot preserves a point-in-time state so you can retrieve an earlier version of a file or folder or roll back a storage unit. This can be faster and more targeted than restoring an entire backup, but the benefit depends on the snapshot still being accessible. If the only snapshot is on the NAS or pool that fails, it may be lost along with the source.
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Snapshot replication: snapshots at another destination
Replication sends snapshots to another pool or NAS, so recovery points can exist outside the original storage pool. QNAP’s QTS 5.0.x documentation distinguishes snapshots alone from local or remote Snapshot Replica in its protection table: for that software version, it lists snapshots alone for accidental modification or deletion and ransomware, and lists local or remote replication additionally for RAID group failure. The table does not mark those configurations as protecting against member-disk failure or disk removal. These are version-specific vendor claims, not a guarantee for every NAS or current configuration.
#1 Best Overall
Sale
TERRAMASTER D4-320 External Hard Drive Enclosure 4-Bay (Diskless)
- High-Speed Data Transmission: The D4-320 hard drive enclosure (a DAS, NOT a NAS) utilizes the USB 3.2 Gen2 protocol, achieving high-speed data transmission of up to 10Gbps. When equipped with four hard drives, the actual read/write speed can reach up to 1,016 MB/s (combined read/write with four SATA III HDDs of 8TB each). With just one SSD installed, the read speed effortlessly reaches 510 MB/s (SATA III 1TB SSD). The D4-320 supports a single HDD up to 30TB, with a total capacity of 120TB, and is compatible with various hard drives, including 3.5-inch SATA hard drives, 2.5-inch SATA hard drives, and 2.5-inch SATA SSDs
- Plug-and-Play Compatibility: The D4-320 USB storage supports 4 individual disks (NO RAID function), and is plug-and-play, eliminating the need for drivers. It is highly compatible with MAC, Windows, and Linux operating systems. The USB Type-C interface supports various computer interfaces, including USB 3.0, USB 3.1, USB 3.2, Thunderbolt 3, and Thunderbolt 4
- Hot Swappable Convenience: The D4-320 HDD enclosure supports hot swapping, allowing users to replace hard disks without powering off the device. This feature enhances convenience and efficiency in data transfer processes
- Tool-Free Hard Drive Management: Featuring a tool-free hard drive tray design, the D4-320 external HDD enclosure enables easy installation and removal of hard drives without requiring additional tools. Furthermore, the D4-320 incorporates TerraMaster's unique Push-lock design, automatically securing the hard drive tray upon insertion, preventing the hard drive from falling out or disconnecting
- Efficient Heat Dissipation and Quieter Operation: The D4-320 direct attached storage incorporates an intelligent temperature-controlled fan for optimal heat dissipation. Additionally, specialized sound-absorbing panels and vibration damping measures contribute to a quieter operation, with noise levels reduced by up to 50% compared to the previous generation. In standby mode, the noise level drops below 21 dB(A), creating a remarkably quiet user environment
Backups: a separate copy for broader recovery
A backup is a copy kept at a destination separate from the source NAS, such as an external device, another NAS, or a cloud service. A separate destination can help when the source NAS is lost or fails, but only if the copy exists, is usable, and has not been affected by the same incident. QNAP’s guidance puts it plainly: “Regular backup is crucial for data protection” (QuTS hero 5.0.x).
Choose protection by the incident you need to recover from
- Some member-disk failures: RAID may preserve availability, depending on its level and configuration. Do not treat that redundancy as a backup.
- An accidental edit or deletion: A retained snapshot can provide a quick route to an earlier version. A backup may also help if it contains a usable earlier copy.
- Ransomware or other unwanted changes: A snapshot can help if a suitable recovery point remains intact and accessible. A separate backup adds another recovery route; its usefulness depends on isolation, retention, and whether the incident reached the backup destination.
- Failure or loss of the NAS or storage pool: A snapshot kept only on that NAS or pool shares the same failure domain. A replica on another NAS or a backup at a separate destination is more independent.
- Theft, fire, or compromise affecting the location: A copy kept off-site can remain available when local devices are lost or inaccessible.
Restore speed and granularity depend on the NAS, the protection method, and how the recovery point was configured. A snapshot is designed for point-in-time rollback; a backup restore uses the copy and destination you configured. Neither label by itself establishes how quickly a particular system can be restored.
Rank #2
Sale
TERRAMASTER F2-425 2-Bay NAS Intel x86 Quad-Core CPU 4GB RAM (Diskless)
- Powerful Performance: Equipped with an Intel x86 quad-core processor and 4GB RAM, the F2-425 network attached storage effortlessly handles 4K transcoding and multitasking. The 2.5GbE port ensures ultra-fast file transfers and supports multi-user concurrent access
- Home Multimedia Hub: The F2-425 media server supports hardware-level 4K H.265 decoding, compatible with Plex, Emby, and Jellyfin for smooth HD video playback, with DLNA for seamless multi-device streaming. The Photos app features AI smart album and efficiently organizes millions of photos
- TNAS Mobile Full Control: Initialize setup for your F2-425 NAS storage via the TNAS Mobile app without a PC. The mobile app supports automatic photo and video backups, plus real-time local/remote synchronization, all managed through a single client
- Ultra-Quiet & User-Friendly: The F2-425 NAS server operates at just 19dB(A), suitable for quiet environments like bedrooms. Its tool-free Push-Lock design HDD trays enable to install HDDs in 10 seconds
- Massive Storage & Security: The F2-425 2-bay NAS supports up to 60TB storage (2 x 30TB for each bay), 50+ independent user accounts, and flexible TRAID arrays, saving 30% more storage space than traditional RAID while ensuring data redundancy. SPC security module and CloudSync (supporting Google Drive, OneDrive, Dropbox) guarantee worry-free data protection. Additionally, TerraSync enables two-way sync between the F2-425 and PCs/Macs
A practical way to combine them
- Configure RAID for the availability you need. Choose a level and layout supported by your NAS and disks, and understand which disk failures that configuration can tolerate. It does not replace a separate copy.
- Retain snapshots for convenient rollback. Set retention to match how far back you may need to recover. Verify your NAS model, filesystem, and software support the snapshot features you intend to use.
- Schedule backups to a separate destination. Use an external device, another NAS, or a compatible cloud service, and monitor the jobs so failures do not go unnoticed. An external USB drive is useful only when paired with a configured backup job and sized for your data and retention needs.
- Keep at least one copy off-site where appropriate. This reduces dependence on equipment and events at one location. Synology and QNAP both recommend the 3-2-1 approach: three total copies, two storage media, and one off-site copy. This is vendor guidance, not a guarantee that a given setup will be safe.
- Check recovery, not just job status. Confirm that the destination contains the expected data and that you know how to restore it. A copy that cannot be accessed or restored is not a useful recovery path.
Check compatibility before choosing snapshot or replication features
Features differ by model, filesystem, and software version. Synology says Snapshot Replication is limited to models that support Btrfs; check the current documentation for your specific device before planning around it. QNAP’s cited protection matrix is for QTS 5.0.x, so it should not be generalized to other QTS releases, QuTS hero, or every model. For backup destinations and tools, consult your manufacturer’s current compatibility and configuration guidance.
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Quick Recap
SaleBestseller No. 3
Bestseller No. 5
Best Value
TERRAMASTER F2-212 2-Bay NAS Quad Core CPU, DDR4 RAM (Diskless)
- Home Network Storage Solution: The F2-212 NAS storage is an affordable and high-performance 2-bay NAS optimized for home and SOHO users, running the latest TOS 7 operating system
- Powerful Hardware Configuration: The F2-212 network attached storage adopts an ARM v8 quad-core 1.7GHz CPU with 1GB RAM (NOT upgradeable). This NAS server features powerful 4K video hardware decoding capability, and is compatible with uPnP/DLNA protocol, making it a solution to serve as home multimedia center
- Across-Platform File Services: The F2-212 file server supports all mainstream file services: SMB, NFS, SFTP/FTP, AFP, iSCSI, WebDAV; and is provided with multiple permission management of users, user groups, and folders, meeting across-platform file services in various network environments
- Rich Backup Solutions: The F2-212 backup solution can provide robust measures for your valuable information by using its visual user interfaces and trustworthy storage solutions thanks to its integration with multiple backup applications such as Duple Backup, TSSS, TFM Backup, CloudSync and more, which can address backup needs in any circumstances
- Simple and Fast System Installation: TerraMaster provides hands-on online tutorials and videos, with a specially designed Default mode to set all configurations to optimal home mode, so all the steps can be completed after the first initial system installation in just a few minutes
Rank #4
Sale
TERRAMASTER F4-425 4-Bay NAS Intel x86 Quad-Core CPU 4GB RAM (Diskless)
- Powerful Performance: Equipped with an Intel x86 quad-core processor and 4GB RAM, the F4-425 network attached storage effortlessly handles 4K transcoding and multitasking. The 2.5GbE port ensures ultra-fast file transfers and supports multi-user concurrent access
- Home Multimedia Hub: The F4-425 media server supports hardware-level 4K H.265 decoding, compatible with Plex, Emby, and Jellyfin for smooth HD video playback, with DLNA for seamless multi-device streaming. The Photos app features AI smart album and efficiently organizes millions of photos
- TNAS Mobile Full Control: Initialize setup for your F4-425 NAS storage via the TNAS Mobile app without a PC. The mobile app supports automatic photo and video backups, plus real-time local/remote synchronization, all managed through a single client
- Ultra-Quiet & User-Friendly: The F4-425 NAS server operates at just 21dB(A), suitable for quiet environments like bedrooms. Its tool-free Push-Lock design HDD trays enable to install HDDs in 10 seconds
- Massive Storage & Security: The F4-425 4-bay NAS supports up to 120TB storage (4 x 30TB for each bay), 50+ independent user accounts, and flexible TRAID / TRAID+ arrays, 30% more storage space than traditional RAID while ensuring data redundancy. SPC module and CloudSync (compatible with Google Drive, OneDrive, Dropbox) enable seamless cross-platform synchronization and uninterrupted data access. Additionally, TerraSync enables two-way sync between the F4-425 and PCs/Macs
Rank #3
Sale
TERRAMASTER D2-320 USB RAID Enclosure 2-Bay (Diskless) | USB 3.2 Gen 2 10Gbps Type C Direct Attached Storage Supports RAID 0, 1, Single, JBOD (Diskless)
- High Speed Data Transmission: The D2-320 hard drive enclosure (a DAS, NOT a NAS) adopts USB 3.2 Gen2 protocol for high-speed data transmission up to 10Gbps. With 2 hard drives in RAID 0, the read/write speed can reach up to 521MB/s (SATA III HDD 8TB x 2). With 2 SSD's in RAID 0, the read speed can reach 1075MB/s (SATA III 1TB SSD x 2)
- Multiple RAID Configurations: The D2-320 is a hardware RAID enclosure and it supports RAID 0, RAID 1, JBOD and SINGLE which can better satisfy various demands of users. In RAID 1, data will be in a mirror backup. When there is a damaged hard drive, you can directly replace the hard drive, and the data will be recovered automatically. This provides an absolute security for the data
- Super-Large Storage Capacity: The D2-320 USB storage enclosure can support up to two 3.5" and 2.5" SATA HDD, as well as 2.5" SATA SSD, with a maximum capacity of 22TB per drive, providing users with up to 44TB (22TB x 2) of storage space
- Intelligent Temperature Control: The D2-320 HDD enclosure has an intelligent temperature-controlled and low-noise fan that automatically adjusts its speed based on the temperature of the hard disk. This feature ensures that the hard disk operates at its best temperature and provides better heat dissipation
- Tool-Free Hard Drive Installation: The D2-320 external hard drive enclosure features a tool-free hard drive tray design that allows for easy installation and removal of hard drives without the need for any tools. Furthermore, the D2-320 incorporates a brand new Push-lock unique design from TerraMaster, which automatically locks the hard drive tray when you insert the hard drive, preventing the hard drive from falling out or disconnecting
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