When a NAS runs short on bays, an expansion unit can add storage without replacing the whole system—but the right choice depends on more than bay count. My leading picks are the Synology DX525 for a straightforward five-bay addition to a compatible DiskStation, the Synology DX1222 for users who need 12 bays and a longer warranty, and the QNAP TL-D810TC4-US for a flexible eight-bay enclosure that can connect to supported computers as well as QNAP NAS devices. Those options solve different capacity and compatibility problems, so I would not treat them as interchangeable.
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The main tradeoffs are host compatibility, connection type, and expansion scale. Synology’s DX units are designed around selected Synology DiskStations and DSM workflows. QNAP’s enclosure uses USB Type-C and lists support for several desktop operating systems, while the Asustor Xpanstor 4 offers a smaller four-bay option with USB 3.2 Gen 2. All five models are diskless, so the drive cost and drive compatibility remain part of the decision. I rank them by how clearly they serve a distinct NAS expansion need—not by raw bay count alone.
Key Takeaways
- Best match for an established Synology setup: The DX525 adds five hot-swappable bays, but buyers must check their DiskStation’s compatibility before ordering.
- Most room in one enclosure: The DX1222 adds 12 drives and carries a five-year limited warranty, though its size and selected-host compatibility make it a specialized choice.
- Most flexible host options: QNAP’s TL-D810TC4-US has eight SATA bays and USB Type-C connectivity, with listed support for QNAP NAS devices and several desktop operating systems.
- Compact four-bay alternative: The Asustor Xpanstor 4 supports SATA HDDs and SSDs and includes MyArchive cold-backup support, but it has fewer bays than the five- and eight-bay picks.
- Legacy-compatible Synology expansion: The DX517 provides five hot-swappable bays over eSATA; its fit depends on a compatible Synology model, so I would verify the host list first.
| Synology DX525 5-Bay Expansion Unit (Diskless) |  | Best Overall for Compatible Synology DiskStations | Drive bays: 5 | Drive support: 3.5-inch or 2.5-inch SATA HDDs and SSDs | Drive inclusion: Diskless | VIEW LATEST PRICE | See Our Full Breakdown |
| Synology DX1222 12-Bay Disk Expansion Unit (Diskless) |  | Best for Large Synology Storage Growth | Drive bays: 12 | Drive compatibility: 2.5-inch or 3.5-inch drives | Drive inclusion: Diskless | VIEW LATEST PRICE | See Our Full Breakdown |
| QNAP TL-D810TC4-US 8-Bay Desktop DAS/JBOD Storage Expansion Enclosure |  | Best for Cross-Platform Expansion | Drive bays: 8 | Drive interface: SATA 6Gb/s | Drive support: 3.5-inch and 2.5-inch SATA HDDs and SSDs | VIEW LATEST PRICE | See Our Full Breakdown |
| Asustor Xpanstor 4 AS5004U 4-Bay NAS Expansion Unit (Diskless) |  | Best Compact Expansion for Asustor Users | Drive bays: 4 | Drive compatibility: 3.5-inch or 2.5-inch SATA HDDs and SSDs | Drive interface: 4 × SATA3 6Gb/s | VIEW LATEST PRICE | See Our Full Breakdown |
| Synology DX517 5-Bay Expansion Unit (Diskless) |  | Best eSATA Expansion for Compatible Older Synology Systems | Drive bays: 5 | Drive support: 2.5-inch and 3.5-inch SATA | Connection: eSATA | VIEW LATEST PRICE | See Our Full Breakdown |
| NAS expansion unit | Drive bays | Warranty | Drive support | Weight |
|---|---|---|---|---|
| Synology DX525 5-Bay Expansion | 5 | 3-year limited hardware warranty | 3.5-inch or 2.5-inch SATA HDDs and SSDs | — |
| Synology DX1222 12-Bay Disk Ex | 12 | 5-year limited warranty | — | 22 pounds |
| QNAP TL-D810TC4-US 8-Bay Deskt | 8 | 2 years | 3.5-inch and 2.5-inch SATA HDDs and SSDs | — |
| Asustor Xpanstor 4 AS5004U 4-B | 4 | 3-year manufacturer warranty | — | 2.3kg |
| Synology DX517 5-Bay Expansion | 5 | 3-year limited warranty | 2.5-inch and 3.5-inch SATA | 8.6 pounds |
More Details on Our Top Picks
Synology DX525 5-Bay Expansion Unit (Diskless)
The DX525 is my best overall pick because its five-bay format makes a substantial but manageable addition to a compatible Synology DiskStation. It accepts 3.5-inch and 2.5-inch SATA HDDs or SSDs, and hot-swappable support helps simplify drive replacement or maintenance. For buyers already using Synology DSM, keeping expansion within the same system family can make more sense than adding a separate enclosure with a different management approach.
Compared with the older DX517, the DX525 is the more direct choice for buyers whose host appears on its supported compatibility list. Both offer five bays and hot-swappable drive support, but the DX517 specifically uses eSATA; the DX525 description emphasizes plug-and-play operation with compatible DiskStations. I would not assume that the newer model works with every Synology NAS, though: compatibility is model-specific, and Synology’s official drive list also limits drive choices.
The tradeoff is straightforward: this is a diskless, host-dependent expansion unit, not a general-purpose storage box. Its three-year limited hardware warranty is a practical point of comparison with the DX1222’s five-year term, and its five bays provide less headroom than either the eight-bay QNAP or 12-bay DX1222. I would choose it when five added bays meet the plan and keeping expansion within a compatible Synology setup matters more than broader host flexibility.
Pros:- Adds five bays for 3.5-inch or 2.5-inch SATA HDDs and SSDs.
- Hot-swappable drive support can simplify maintenance.
- Designed for plug-and-play expansion with compatible Synology DiskStations.
- Includes a three-year limited hardware warranty.
Cons:- Disk drives are not included.
- Compatibility is limited to supported Synology models and official drive-list requirements.
- Offers fewer bays than the QNAP TL-D810TC4-US or Synology DX1222.
Best for: Synology DiskStation owners who have confirmed DX525 compatibility and want five hot-swappable SATA bays managed within their NAS environment.
Not ideal for: Buyers with an unsupported NAS, those who need a computer-friendly standalone enclosure, or anyone seeking more than five added bays.
- Drive bays:5
- Drive support:3.5-inch or 2.5-inch SATA HDDs and SSDs
- Drive inclusion:Diskless
- Drive handling:Hot-swappable
- Host compatibility:Selected Synology DiskStation models
- Management:Synology DSM tools
- Warranty:3-year limited hardware warranty
Our verdict“I recommend the DX525 as the most balanced choice for buyers who want five additional bays and have verified that their Synology DiskStation supports it.”
Synology DX1222 12-Bay Disk Expansion Unit (Diskless)
When five more bays are not enough, the DX1222 gives a compatible Synology DiskStation room to grow by up to 12 drives. That scale is its defining advantage over the DX525 and DX517: rather than adding a small extension, it supports a larger expansion plan in one enclosure. Synology DSM volume-management tools also keep it within the management environment many existing Synology owners already use.
This is the premium capacity choice in this lineup, and the five-year limited warranty is longer than the three-year terms listed for the DX525, DX517, and Asustor Xpanstor 4. Its metal construction and 22-pound listed weight point to a substantial unit, so I would plan for a suitable permanent placement rather than treating it like a small desktop accessory. The 12-bay capacity also brings more drive purchasing and configuration decisions than the five-bay models.
The main drawback is that the DX1222 only serves selected Synology DiskStation units, and it ships without drives. It is not a universal enclosure for a PC or another NAS brand. Compared with QNAP’s eight-bay USB-connected enclosure, the DX1222 offers four more bays and DSM-oriented management, while QNAP lists broader operating-system support. I would select the DX1222 when host compatibility is confirmed and a large, integrated Synology expansion matters more than general-purpose connectivity or a smaller footprint.
Pros:- Adds up to 12 drives to compatible Synology DiskStation systems.
- Supports 2.5-inch and 3.5-inch drives.
- Works with Synology DSM volume-management tools.
- Includes a five-year limited warranty.
Cons:- Disk drives are not included.
- Works only with selected Synology DiskStation models.
- Its 22-pound weight and 12-bay scale may be excessive for modest expansion plans.
Best for: Synology users planning a major increase in drive capacity who can confirm support for their DiskStation and want DSM-based volume management.
Not ideal for: Owners of other NAS brands, buyers who only need a few extra bays, or anyone needing a lightweight enclosure that works across desktop operating systems.
- Drive bays:12
- Drive compatibility:2.5-inch or 3.5-inch drives
- Drive inclusion:Diskless
- Host compatibility:Selected Synology DiskStation systems
- Management:Synology DSM volume management
- Weight:22 pounds
- Enclosure:Metal; black
- Warranty:5-year limited warranty
Our verdict“I would choose the DX1222 for large-scale Synology expansion when its 12 bays and longer warranty justify a sizeable, model-specific unit.”
QNAP TL-D810TC4-US 8-Bay Desktop DAS/JBOD Storage Expansion Enclosure
The QNAP TL-D810TC4-US is the most flexible host option in this group according to its listed compatibility: QNAP NAS devices, Windows, macOS, Ubuntu, and Linux. Its eight SATA bays give it more capacity than the four- and five-bay options, while USB Type-C makes it a different kind of fit from Synology’s model-specific DX units. That combination suits buyers who may want to attach storage to a compatible NAS or a desktop system rather than commit to one vendor’s expansion ecosystem.
Its stated USB transfer rate is up to 10Gbps, and the enclosure supports 3.5-inch and 2.5-inch SATA HDDs and SSDs. QNAP utilities provide drive monitoring and JBOD management. These details make it more than a simple bay count comparison: buyers need to decide whether a USB-connected DAS/JBOD workflow meets their needs, or whether they specifically require a matched NAS expansion unit managed as part of their NAS platform. I would check the supported mode and host documentation for the intended setup before buying.
There is an unusual specification caveat: the product description also mentions a USB 4 interface and speeds up to 40Gbps, which conflicts with the listed up-to-10Gbps USB Type-C specification. I would not plan around the higher claim without confirmation. The two-year warranty is also shorter than the three-year terms on DX525 and Xpanstor 4, and drives are not included. Compared with Synology’s DX1222, QNAP offers broader listed computer support and eight rather than 12 bays; the DX1222 is the clearer choice for a compatible Synology-only expansion plan.
Pros:- Provides eight bays for 3.5-inch or 2.5-inch SATA drives.
- Lists compatibility with QNAP NAS, Windows, macOS, Ubuntu, and Linux.
- USB Type-C connection has a listed transfer rate of up to 10Gbps.
- QNAP utilities support drive monitoring and JBOD management.
Cons:- Disk drives are not included.
- The description conflicts on USB speed, so the higher 40Gbps claim needs confirmation.
- Two-year warranty is shorter than several alternatives in this lineup.
Best for: Buyers who need eight SATA bays and want a USB Type-C enclosure listed for QNAP NAS devices and multiple desktop operating systems.
Not ideal for: Those who need a guaranteed 40Gbps connection, a longer stated warranty, or a dedicated expansion unit for a Synology DiskStation.
- Drive bays:8
- Drive interface:SATA 6Gb/s
- Drive support:3.5-inch and 2.5-inch SATA HDDs and SSDs
- Connection:USB Type-C
- Listed transfer rate:Up to 10Gbps
- Listed host support:QNAP NAS, Windows, macOS, Ubuntu, and Linux
- Form factor:Tabletop
- Warranty:2 years
Our verdict“I recommend the TL-D810TC4-US when eight bays and wider listed host support matter more than a single-vendor NAS expansion design.”
Asustor Xpanstor 4 AS5004U 4-Bay NAS Expansion Unit (Diskless)
The Xpanstor 4 is the compact, four-bay choice for an Asustor-compatible NAS or PC setup. It supports 3.5-inch and 2.5-inch SATA HDDs and SSDs and connects through USB 3.2 Gen 2 Type-C, with a listed 10Gbps transfer rate. Compared with the QNAP’s eight bays, this unit gives up capacity in exchange for a smaller step up in storage; compared with Synology’s five-bay DX models, it offers USB connectivity and Asustor-specific features such as MyArchive cold backup.
Its MyArchive support and smart power synchronization make it a more tailored option for buyers already working with Asustor. Temperature-controlled fan operation is another useful enclosure feature, though it does not change the central compatibility question: the description names a compatible NAS or PC, so I would verify the exact host and intended storage mode before purchase. The enclosure is diskless, meaning the buyer chooses and supplies all four drives.
Four bays will be enough for a modest expansion but leave less room for growth than the DX525, DX517, QNAP, or DX1222. Its three-year manufacturer warranty matches the DX525 and exceeds QNAP’s listed two years, while remaining shorter than the DX1222’s five-year term. I would pass on it if my plan already needs eight or more drives, or if I need a Synology-specific expansion unit. For an Asustor-focused setup that benefits from cold-backup support and Type-C connectivity, it fills a distinct smaller-capacity role.
Pros:- Adds four bays for 3.5-inch or 2.5-inch SATA HDDs and SSDs.
- USB 3.2 Gen 2 Type-C connection lists a 10Gbps transfer rate.
- Supports Asustor MyArchive cold backup.
- Includes smart power synchronization and temperature-controlled fan operation.
Cons:- Disk drives are not included.
- Four bays provide less expansion room than the five-, eight-, and 12-bay alternatives.
- Host compatibility should be verified for the intended NAS or PC setup.
Best for: Asustor users who want four SATA bays, USB Type-C connectivity, and MyArchive cold-backup support in a smaller expansion step.
Not ideal for: Buyers planning high-capacity growth, those who need a Synology-specific DX unit, or anyone expecting drives to be included.
- Drive bays:4
- Drive compatibility:3.5-inch or 2.5-inch SATA HDDs and SSDs
- Drive interface:4 × SATA3 6Gb/s
- USB interface:USB 3.2 Gen 2 Type-C
- Listed transfer rate:10Gbps
- Maximum supported drive capacity:22TB
- Weight:2.3kg
- Warranty:3-year manufacturer warranty
Our verdict“I would pick the Xpanstor 4 for a modest Asustor-oriented expansion where MyArchive and USB Type-C matter more than maximum bay count.”
Synology DX517 5-Bay Expansion Unit (Diskless)
The DX517 remains a useful five-bay Synology expansion option where its eSATA connection matches a compatible DiskStation. It accepts 2.5-inch and 3.5-inch SATA drives in hot-swappable trays and can be used for added storage or local backup. For buyers with a supported host, it keeps the expansion path within Synology’s ecosystem and offers the same basic five-bay scale as the DX525.
The distinction between the two five-bay models is the reason to choose carefully. The DX517’s stated eSATA connection may make it the relevant fit for a compatible setup that calls for that interface, while the DX525 is described as a plug-and-play unit for its supported DiskStations and has an explicit official-drive-list restriction. Neither model should be treated as universally compatible. I would check the exact NAS model and supported expansion-unit documentation before settling on either one.
The DX517 has hot-swappable trays and supports storage expansion or local backup, but its listing gives a 220 megabits-per-second transfer-rate figure that is not directly comparable to the QNAP and Asustor USB gigabit-rate claims without matching test conditions. I would avoid using that number alone to predict performance. The unit is diskless and has a three-year limited warranty; it also adds only five bays, so the DX1222 is a better fit for a large growth plan. I rank the DX517 below the DX525 because its eSATA-based fit is more specific, not because five bays are inherently inadequate.
Pros:- Adds up to five bays to compatible Synology DiskStation systems.
- Supports 2.5-inch and 3.5-inch SATA drives.
- Hot-swappable trays support easier drive replacement.
- Can serve storage expansion or local backup needs.
Cons:- Disk drives are not included.
- Compatibility depends on the specific Synology NAS model.
- Uses eSATA rather than the USB Type-C connection listed for QNAP and Asustor.
Best for: Owners of a compatible Synology DiskStation that specifically supports the DX517 and need five eSATA-connected hot-swappable bays.
Not ideal for: Buyers whose Synology NAS is not on the compatible list, those seeking USB Type-C host flexibility, or users planning 12-drive expansion.
- Drive bays:5
- Drive support:2.5-inch and 3.5-inch SATA
- Connection:eSATA
- Drive trays:Hot-swappable
- Listed transfer rate:220 megabits per second
- Dimensions:9.76 × 9.17 × 6.18 inches
- Weight:8.6 pounds
- Warranty:3-year limited warranty
Our verdict“I would choose the DX517 only when a compatible Synology host calls for this eSATA five-bay unit, rather than defaulting to it over the DX525.”
How We Picked
I ranked these units by their usefulness as NAS expansion hardware, not by how impressive an isolated specification sounds. The first filter is host fit: a purpose-built expansion unit only helps if the existing NAS supports it. Synology’s DX517, DX525, and DX1222 all depend on compatible DiskStation models, so I distinguish them by bay count, connection details, warranty, and the scale of expansion each serves. For the QNAP and Asustor units, I also weigh their stated USB host options and whether that flexibility suits a mixed NAS-and-computer setup.
Next, I compared capacity and drive flexibility. Five bays can be a sensible step up when a NAS needs more room without a large enclosure; eight or 12 bays suit users planning a more substantial expansion. Support for both 2.5-inch and 3.5-inch SATA drives broadens drive choices, but none of these products includes drives. I treat diskless status as a practical cost and setup factor rather than a flaw by itself, since buyers may want to select their own drives.
I also looked at connection limits and management expectations. The DX517 uses eSATA, while QNAP and Asustor list USB Type-C connections with transfer-rate claims. Those numbers should not be mistaken for a guarantee of real-world performance: drive type, host connection, workload, and configuration all matter. The QNAP listing contains conflicting USB speed descriptions, so I rely on the stated up-to-10Gbps specification rather than assuming a higher figure. Finally, I considered warranty terms, physical scale, and the tradeoffs that might make a model a poor fit. This ranking favors clearly defined roles and calls out where buyers should confirm compatibility before purchasing.
Factors to Consider When Choosing Best NAS Expansion Unit
My first buying question is not how many bays I can fill; it is whether the enclosure will work with the NAS I already own. After that, I match the drive count, connection, and management style to the kind of expansion I need.
Check host compatibility before bay count
Expansion units are not automatically universal. Synology’s DX517, DX525, and DX1222 work with selected DiskStation models, and the appropriate unit depends on the host’s supported expansion options. The same caution applies to the QNAP and Asustor products: their listed computer or NAS support does not prove that every setup mode works with every device. I would check the manufacturer’s current compatibility information for both the enclosure and the drives I intend to install. If the NAS model is unsupported, extra bays do not help.
This check also clarifies whether I want a matched NAS expansion unit or a USB-connected DAS/JBOD enclosure. The Synology DX models are the clear candidates for a supported Synology environment. QNAP lists multiple desktop operating systems in addition to QNAP NAS devices; Asustor describes use with a compatible NAS or PC and adds its own MyArchive feature. I would buy according to the actual host workflow, not just a broad compatibility phrase.
Choose enough bays without buying empty capacity
Four or five bays suit a moderate expansion; eight or 12 bays are better when the storage plan already calls for many drives. The Xpanstor 4 is the smallest addition here. DX517 and DX525 each add five bays, while QNAP gives eight and DX1222 reaches 12. More bays can reduce the need to add another enclosure soon, but they also mean more drives to source, configure, and maintain. I would estimate the usable capacity I need and leave room for the storage arrangement my NAS supports, rather than treating every drive’s capacity as immediately available user space.
Drive counts also affect the physical setup. The DX1222 weighs 22 pounds and is a substantial enclosure; the DX517 is listed at 8.6 pounds, and the Xpanstor 4 at 2.3kg. The provided specifications do not give comparable dimensions for every model, so I would confirm the product footprint before choosing a shelf or desk location. Larger capacity can be worthwhile, but only if there is a stable place and suitable power for the unit.
Understand the connection and speed claims
Connection type shapes compatibility and expectations. The DX517 uses eSATA; QNAP lists USB Type-C at up to 10Gbps; Asustor lists USB 3.2 Gen 2 Type-C at 10Gbps. The DX525 and DX1222 descriptions emphasize their compatible Synology systems and DSM workflow rather than giving a comparable host-interface speed figure. These specifications should not be lined up as if they were identical performance tests. Actual throughput depends on the host, installed drives, connection, and workload.
The QNAP description contains conflicting information: one specification states up to 10Gbps, while another passage refers to USB 4 and up to 40Gbps. I would use the clearly listed 10Gbps figure for planning and seek confirmation if a higher rate affects the purchase. The DX517’s listed 220 megabits per second is also a different unit and should not be compared casually with gigabits-per-second claims. For a NAS expansion decision, verified host support and the expected workload matter more than an isolated headline number.
Decide whether you need NAS-managed expansion or DAS/JBOD
A DAS/JBOD enclosure is not automatically the same as a NAS volume expansion unit. QNAP calls its model a desktop DAS/JBOD storage expansion enclosure and lists utilities for monitoring drives and managing JBOD configurations. Synology describes its DX units in relation to DiskStation expansion and DSM volume management. Asustor highlights NAS or PC use and MyArchive cold backup. Those distinctions affect how storage is presented and managed, so I would confirm the exact mode before buying—especially if I need a particular RAID, backup, or shared-storage workflow.
For a Synology owner seeking integrated DSM management, I would start with the compatible DX option. If I need an enclosure that can connect to different kinds of hosts, QNAP’s stated operating-system support may be a better match, subject to checking the intended mode. Asustor’s cold-backup feature can suit a specific archive routine. The right category is the one that fits the host and workflow, not the one with the broadest feature list.
Budget for drives and verify the drive list
All five products are diskless, so the total build requires separately selected drives. This gives me control over capacity and whether to use HDDs, SSDs, or a mixture where the enclosure and host support that plan. The Synology DX525 calls out Synology’s official compatibility list, making drive verification especially important. For all models, I would confirm drive size, interface, and supported capacity rather than assuming any SATA disk will be accepted or behave as intended.
Capacity figures need context. The Xpanstor 4 lists a maximum supported hard disk capacity of 22TB, but that is a product specification, not a promise about usable volume size or compatibility with every drive and host configuration. RAID or other storage arrangements can also affect available space. I would check the drive list and NAS documentation, then choose a drive plan that fits both the enclosure and the expansion software.
Compare warranty and ongoing maintenance
Warranty length is one practical differentiator: the DX1222 lists five years, DX525 and DX517 list three years, Asustor lists a three-year manufacturer warranty, and QNAP lists two years. Warranty terms are only one part of long-term ownership, but they can help separate otherwise similar choices. I would review the terms that apply in my region and make sure the purchase channel provides the support path I expect.
Hot-swappable trays on the Synology DX models can make replacing a drive simpler, though hot-swap support does not remove the need for backups or careful storage management. QNAP offers drive monitoring utilities, and Asustor includes temperature-controlled fan operation and smart power synchronization. These features address different parts of maintenance; I would prioritize the ones tied to my workflow rather than treating them as equivalent benefits.
Frequently Asked Questions
Can I use any NAS expansion unit with any NAS?
No. Host compatibility is model-specific, particularly for the Synology DX517, DX525, and DX1222, which support selected DiskStation systems. QNAP and Asustor list broader host types, but that still does not guarantee every feature or storage mode works with every NAS or computer. I would check the enclosure’s current compatibility information against the exact host model before buying.
Do these NAS expansion units include hard drives?
No. All five models in this guide are diskless, so I would plan to buy compatible HDDs or SSDs separately. That allows the buyer to choose drive capacity and type, but it also means the complete storage setup requires more than the enclosure itself. Check the relevant host and enclosure documentation for supported drives, capacity limits, and any official compatibility-list requirements.
Which unit offers the most expansion capacity?
The Synology DX1222 adds up to 12 drives, the largest bay count in this roundup. That makes it the leading option for a substantial expansion plan, provided the DiskStation is compatible. QNAP’s TL-D810TC4-US has eight bays and lists multiple desktop operating systems as well as QNAP NAS devices, which may suit buyers who value host flexibility more than the DX1222’s additional four bays.
Is USB Type-C always faster or better than eSATA?
Not by itself. Connection claims need to be read alongside host support and workload. The Asustor lists USB 3.2 Gen 2 Type-C at 10Gbps, and QNAP lists USB Type-C up to 10Gbps while its description also makes a conflicting higher-speed claim. The DX517 uses eSATA, with a separate listed transfer-rate figure. I would confirm what the host supports and avoid comparing unlike specifications as if they came from the same test.
Should I choose a five-bay unit or a larger enclosure?
I would choose based on the storage plan and host, not bay count alone. Five bays are a reasonable middle ground when the immediate need is moderate and the Synology host supports a DX525 or DX517. The QNAP’s eight bays and Synology DX1222’s 12 bays better serve larger growth plans, while the Asustor’s four bays suit a smaller addition. More bays can leave room for future drives, but they also increase the number of drives to buy, configure, and maintain.
Conclusion
For most buyers who already own a compatible Synology DiskStation, I would start with the DX525: its five bays, hot-swappable support, and DSM-oriented fit make it the most balanced choice here. If the NAS specifically calls for an eSATA expansion unit, the DX517 is the targeted alternative; I would not choose it without checking the host model first. For a larger Synology storage plan, the DX1222 is the clear capacity pick, with 12 bays and a five-year limited warranty, but it is not a general-purpose enclosure.
Buyers who want a broader range of listed host options should compare the QNAP TL-D810TC4-US and Asustor Xpanstor 4. QNAP is better suited to an eight-bay USB-connected DAS/JBOD setup that may attach to a QNAP NAS or supported desktop system; verify the conflicting speed details before relying on a higher connection claim. Asustor is the more compact four-bay choice for users who value MyArchive cold backup and Asustor-oriented features. Across every pick, my final step would be the same: confirm host and drive compatibility, then plan for the drives themselves. Each unit is diskless, and the best enclosure is the one that fits the NAS and storage workflow already in place.
