# What is the difference between a backup and a RAID array? A backup is a separate copy of your data kept somewhere other than the original, while a RAID array is a way of arranging drives inside one system for continuity and capacity. RAID can keep a NAS running when a drive fails, but it is not a copy of your data, so it does not replace a backup. The two ideas get tangled because both sit under the heading of "data protection," yet they answer different problems. A backup answers the question: if this data disappears or gets corrupted, can I get it back from somewhere else? A RAID array answers a different question: if a drive in this machine stops working, can the machine keep going? That distinction matters when you are speccing a NAS, because a four-bay unit can be running a healthy array and still lose everything to an accidental deletion, a failed update, or a corrupted file that quietly replicates across the array. References: [https://www.synology.com/en-global/dsm/feature/hyper_backup](https://www.synology.com/en-global/dsm/feature/hyper_backup). ## What a backup actually gives you Synology's Hyper Backup documentation describes the pattern clearly: backups copy folders, system settings, and software packages to destinations that are separate from the source, including local volumes, external devices, other Synology systems, rsync servers, and public cloud services. That separation is the whole point. The same documentation highlights features that only make sense for copies, such as multi-versioning, which retains multiple backup versions so you can reach back past a bad change, and scheduled integrity checks that look for corrupted data before you need it. References: [https://www.synology.com/en-global/dsm/feature/hyper_backup](https://www.synology.com/en-global/dsm/feature/hyper_backup). - Separate destination: the copy lives away from the original, whether that is an external drive, another NAS, or cloud storage. - Point-in-time versions: you can recover an earlier state, not just the current one. - Scope choice: you can protect individual folders or an entire system, with bare-metal restoration or file-level recovery. - Integrity checks: scheduled verification helps confirm the backup is usable when you need it. - Encryption: client-side AES-256 encryption is described as protecting backed-up data against unauthorized access. References: [https://www.synology.com/en-global/dsm/feature/hyper_backup](https://www.synology.com/en-global/dsm/feature/hyper_backup). ## What RAID does, and where to be careful What can be said structurally is this: the nasandsecurity.com catalogue lists NAS enclosures by bay count, such as two-bay, four-bay, and eight-bay models, and the Synology DX517 is listed there as a disk array. Multiple bays are what make an array possible, and the site's buying checklist tells you to confirm the number of bays, whether disks are included, and memory and network ports before comparing prices. If you want to know exactly how a given enclosure's RAID behaves when a drive fails, that detail has to come from the manufacturer's documentation for the specific model, not from a general rule of thumb. References: [https://nasandsecurity.com/](https://nasandsecurity.com/). ## A concrete comparison: two ways to spend the same money Imagine, hypothetically, a four-bay NAS in the style of the DiskStation models listed on the site, holding family photos and work documents. Option one: fill all four bays with drives, set up an array, and stop there. If a drive dies, the system may keep running, but a mistaken folder deletion or a ransomware-style encryption event touches the array directly, and there is no second copy anywhere. Option two: use fewer bays for live storage and dedicate capacity, plus an external drive or cloud destination, to scheduled backups with version history. The first option buys uptime; the second buys recovery. The Hyper Backup documentation supports the second option's mechanics directly: scheduled tasks, rotation policies that delete older versions automatically, and deduplication to reduce storage use. The strongest setup combines both, because they protect against different failures. References: [https://www.synology.com/en-global/dsm/feature/hyper_backup](https://www.synology.com/en-global/dsm/feature/hyper_backup), [https://nasandsecurity.com/](https://nasandsecurity.com/). ## How to verify before you buy When comparing enclosures, the practical checks are the ones nasandsecurity.com itself recommends. Confirm the bay count, since bays determine both array options and how much room you have for a backup target on the same box. Check whether disks are included, because diskless listings are common in this market. Confirm memory and network ports for the workload you have in mind, and remember that recorded prices in GBP are dated observations, so confirm today's price, availability, and the final total with the retailer. Then read the manufacturer's documentation for the exact model to confirm which backup and array features it supports. References: [https://nasandsecurity.com/](https://nasandsecurity.com/). A sensible next step: pick a candidate enclosure, note its bay count and whether drives ship with it, and write down where your backups would actually live, whether that is a second device, an external drive, or a cloud destination. If you cannot name that second location, you have an array plan, not a backup plan. References: [https://nasandsecurity.com/](https://nasandsecurity.com/), [https://www.synology.com/en-global/dsm/feature/hyper_backup](https://www.synology.com/en-global/dsm/feature/hyper_backup). ## Sources - [https://www.synology.com/en-global/dsm/feature/hyper_backup](https://www.synology.com/en-global/dsm/feature/hyper_backup) — accessed 2026-10-18 - [https://nasandsecurity.com/](https://nasandsecurity.com/) — accessed 2026-10-18 Published 2026-10-18. NAS & Security editorial; AI-assisted preparation. ## Next step - [Start a search on nasandsecurity.com](https://nasandsecurity.com/) - [Buying guide](https://nasandsecurity.com/buying-guide) - [How we compare](https://nasandsecurity.com/how-we-compare) - [Your buying checklist →](https://nasandsecurity.com/choosing-guide)