Product Description
Synology DX517 5-Bay Desktop Storage Expansion Unit for DiskStation NAS
Scale your Synology DiskStation without disrupting operations. The Synology DX517 adds five additional 3.5"/2.5" SATA drive bays to compatible DiskStation NAS systems through a single eSATA connection, enabling seamless online volume expansion or a dedicated local backup destination. Hot-swappable trays, screwless installation, and full management from DiskStation Manager make the DX517 the simplest way to grow your NAS storage capacity as your needs evolve.
Simple Capacity Expansion for Your Synology DiskStation
The Synology DX517 is designed for one purpose: making it straightforward to grow your NAS storage without complexity or downtime. Connect it to a compatible DiskStation via eSATA, and the additional five bays appear immediately in DiskStation Manager — ready to expand an existing RAID volume or serve as a standalone local backup destination. Furthermore, the hot-swappable tray design means drives can be installed or replaced at any time without shutting down the system.
The DX517's most valuable capability is online volume expansion, managed entirely from DiskStation Manager on the host NAS. Once connected, the additional bays are immediately available to extend an existing storage pool or RAID volume without interrupting active services, shared folders, or user access. This means your NAS continues operating normally throughout the expansion process — no scheduled maintenance windows or service interruptions required.
The DX517 can alternatively be configured as a separate, dedicated local backup volume for the host DiskStation. Creating a distinct volume on the expansion unit means backup data is isolated from primary storage — so in the event of a primary drive failure, your backup archive remains intact and immediately accessible. This is a practical implementation of the 3-2-1 backup principle for users who want local redundancy without additional standalone NAS hardware.
Every drive bay in the DX517 features a hot-swappable, screwless tray design. Drives can be installed or removed without tools and without powering down the system. This simplifies both the initial setup — where multiple drives can be installed in minutes — and ongoing maintenance, where a failed drive can be swapped during normal operation to begin RAID rebuilding immediately. Furthermore, the tray mechanism accepts both 3.5" and 2.5" SATA drives without adapters.
There is no separate management interface for the DX517 — everything is handled from DSM on the host NAS. Storage pool creation, RAID configuration, volume expansion, drive health monitoring, and status alerts all appear natively within the DiskStation Manager interface you already use. This unified management approach eliminates the complexity of administering a separate device and ensures consistent monitoring across both the host NAS and expansion unit from a single dashboard.
The DX517 accepts both 3.5" and 2.5" SATA drives, giving you full flexibility over your storage configuration. Use high-capacity 3.5" NAS HDDs such as Seagate IronWolf, WD Red Plus, or Toshiba N300 for maximum storage density. Alternatively, populate bays with 2.5" SATA SSDs for a high-performance storage pool or SSD read/write cache. This flexibility allows the same expansion unit to serve different roles as your storage requirements change over time.
The DX517 is compatible with surveillance-grade HDDs, making it a suitable expansion solution for Synology NAS systems running Surveillance Station. Drives such as WD Purple or Seagate SkyHawk can be used in the expansion unit to provide dedicated, high-capacity storage for continuous camera recording streams. Additionally, the DX517 supports SSD caching when configured appropriately on the host DiskStation, improving overall system responsiveness across connected services.
Grow Your NAS Without Starting Over
The DX517 connects to your existing DiskStation and makes five additional drive bays immediately available — without reinstalling, reformatting, or interrupting a single service running on your NAS.
Online Expansion
Add capacity to a live RAID volume without shutting down or losing access
Hot-Swap Trays
Install or replace drives at any time — no tools, no downtime
DSM Managed
Fully controlled from DiskStation Manager — no extra software needed
Backup Ready
Create a separate local backup volume isolated from primary storage
Compatible Synology DiskStation Models
The DX517 supports volume expansion across compatible DiskStation models. Always verify compatibility with your specific model on the Synology compatibility list before purchase.
Technical Specifications
| Feature | Specification |
|---|---|
| Model | Synology DX517 |
| Form Factor | Desktop |
| Drive Bays | 5 |
| Drive Compatibility | 3.5" and 2.5" SATA HDD / SSD |
| Host Interface | eSATA (connects to host DiskStation) |
| Hot-Swappable | Yes – screwless tray design |
| Volume Expansion | Online – no service interruption required |
| Management | DiskStation Manager (DSM) on host NAS |
| Use Cases | RAID volume expansion, dedicated local backup, surveillance storage, SSD cache (host-dependent) |
| System Synchronisation | Synchronised operation with host DiskStation |
| Power Supply | External power adapter (included) |
| Cooling | System fan(s) with variable speed |
| Dimensions (H x W x D) | 166 x 182 x 233.2 mm |
| Weight | 2.29 kg (without drives) |
Frequently Asked Questions
Can I use regular desktop hard drives in the DX517? ▼
While regular desktop drives can function in a NAS environment, it is recommended to use NAS-optimised HDDs such as Seagate IronWolf, WD Red Plus, or Toshiba N300. These drives are engineered for 24/7 operation, data redundancy, and vibration resistance — all important for reliable NAS performance over extended periods.
What is the difference between NAS HDDs and Surveillance HDDs? ▼
NAS HDDs are designed for data storage, backups, and multi-user file sharing. Surveillance HDDs such as WD Purple and Seagate SkyHawk are optimised specifically for the sustained, continuous write workloads generated by multi-camera security systems. If you plan to use the DX517 as a surveillance recording destination, surveillance-grade drives are the more appropriate choice.
How do RAID configurations improve data security in NAS systems? ▼
RAID distributes or mirrors data across multiple drives to provide fault tolerance. If one drive fails in a RAID 1 (mirroring) or RAID 5 (striping with parity) configuration, the system continues to operate and your data remains intact while the failed drive is replaced and rebuilt. This protects against the most common cause of data loss: individual drive failure.
Can the DX517 handle surveillance workloads? ▼
Yes. The DX517 supports surveillance-grade HDDs and is compatible with Synology NAS systems running Surveillance Station. It can serve as dedicated surveillance storage when configured as a separate volume, providing isolated recording capacity that does not compete with primary NAS storage.
Does the DX517 support SSD caching? ▼
Yes, the DX517 supports SSD caching when the host DiskStation is configured to use it. SSD read/write caching can improve overall system responsiveness by serving frequently accessed data from faster flash storage rather than spinning HDDs.
Can I expand my storage without interrupting active services? ▼
Yes. The DX517 is designed for online, on-the-fly volume expansion. Once connected and recognised by DSM, you can add drives to an existing storage pool and expand volumes while the NAS continues serving files, running applications, and recording footage — without any service interruption or scheduled downtime.
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