Synology DS1520+ DiskStation 5-Bay NAS (Diskless) — main product image

Synology DS1520+ DiskStation 5-Bay NAS (Diskless)

Synology

Synology DS1520+ DiskStation 5-Bay NAS (Diskless)

Name: Synology DS1520+ DiskStation 5-Bay NAS (Diskless)
Brand: Synology
SKU: DS1520+

★★★★★4.8 (567 reviews)

3.5 inch2.5 inch

A five-bay NAS with NVMe cache acceleration that grows from small-office storage to a 108TB data infrastructure without swapping hardware.

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Overview

The Synology DS1520+ is a five-bay network-attached storage unit built around a scalable architecture that addresses a specific gap in the small-office NAS market: the ability to start with a manageable capacity footprint and grow to 15 drives without replacing the base unit. Its Celeron J4125 processor, paired with 8GB DDR4 and dedicated M.2 2280 NVMe cache slots, is calibrated for mixed workloads — simultaneous SMB file sharing, backup jobs via Hyper Backup, and light Docker container workloads are all within its operational envelope. The NVMe cache slots deserve specific attention: they allow cache-tier acceleration without the bay-count penalty that plagues units where cache drives compete with storage drives for physical slots.

The DS1520+ is built for small IT teams and technically proficient small offices that need a centralized data platform they can actually manage without enterprise licensing overhead. Synology's DSM operating system is the real product here — a full NAS OS with a curated package ecosystem covering surveillance (Surveillance Station), cloud sync, virtualization (Virtual Machine Manager), and snapshot-based protection. The hardware is sized to run that software stack reliably over a multi-year deployment. At full 15-drive expansion, each internal volume can reach 108TB — a ceiling that most small offices won't approach, but its existence means the DS1520+ is a platform decision, not a capacity decision you'll need to revisit in 18 months.

Key Features

Capacity-scalable NAS with SSD Cache Acceleration Capability. Compatible Drive Type-3.5 inch SATA HDD, 2.5 inch SATA HDD, 2.5 inch SATA SSD, M.2 2280 NVMe SSD. "Compatible drive type" indicates drives that have been tested to be compatible with Synology products. This term does not indicate the maximum connection speed of each drive bay. Each internal volume (may consist of multiple drives) is expandable up to 108TB

Flexibly scale up to fifteen drives to increase storage capacity as demand grows

Built-in M.2 2280 NVMe SSD slots permit cache acceleration without occupying storage drive bays

Back up critical data and reduce Recovery Time Objective (RTO) with Snapshot Replication

Accelerated Application Performance Average 16% performance boost to photo indexing and other computing-intensive operations, as well as database response time

Specifications

Drive Bays

Compatible Drive Types

3.5 inch SATA HDD, 2.5 inch SATA HDD, 2.5 inch SATA SSD, M.2 2280 NVMe SSD

Max Internal Volume Capacity

108TB

SSD Cache Slots

Built-in M.2 2280 NVMe SSD slots

Performance Boost

Average 16% to photo indexing and computing-intensive operations

Pros & Cons

👍 Pros

Dedicated M.2 NVMe cache slots accelerate array performance without sacrificing any of the five SATA storage bays — a genuine engineering advantage over NAS units that force a cache vs. capacity trade-off.
Expansion to 15 drives via eSATA units makes the DS1520+ a credible long-term platform rather than a box you'll outgrow in two years.
Snapshot Replication delivers enterprise-grade ransomware protection at no additional software cost, a critical feature for small offices without dedicated IT staff.
DSM (DiskStation Manager) is one of the most mature NAS operating systems available, with a well-documented package ecosystem covering surveillance, virtualization, and backup workloads.
8GB DDR4 base memory is sufficient headroom for multi-user SMB shares and light virtualization without an immediate upgrade.

👎 Cons

Diskless pricing means total cost of ownership is substantially higher once drives are factored in — five enterprise HDDs can easily double or triple the unit cost.
No 10GbE networking onboard; at gigabit speeds, the NVMe cache delivers diminishing returns for users transferring large files over the LAN regularly.
The M.2 cache tier helps with random I/O and indexed tasks but does not close the gap with all-SSD NAS units for sustained sequential write workloads.
Expansion unit compatibility is limited to Synology's own DX517 — you cannot attach third-party JBOD enclosures to scale beyond the 5-bay base.

Frequently Asked Questions

What does the built-in M.2 NVMe caching actually do for read/write performance?

The M.2 slots allow you to install NVMe SSDs as a read-write cache tier that sits in front of your spinning disk array. Synology's testing shows roughly a 16% average boost on compute-heavy operations like photo indexing and database queries — more importantly, it does this without consuming any of your five SATA bays, preserving full storage capacity.

What drive types are confirmed compatible with the DS1520+?

Synology has tested and validated 3.5" SATA HDDs, 2.5" SATA HDDs, 2.5" SATA SSDs, and M.2 2280 NVMe SSDs (in the cache slots). Note that the drive bays' maximum connection speed is determined by their SATA interface — NVMe speed is only available through the dedicated M.2 slots.

How does the expansion path to 15 drives work?

The DS1520+ supports up to two Synology DX517 expansion units via eSATA, adding five bays each. That takes the total from 5 to 15 drives. Each internal volume can grow up to 108TB, so the expansion path is meaningful — not just a marketing ceiling.

Is Snapshot Replication included, or is it a paid add-on?

Snapshot Replication is a first-party Synology package available through DSM's Package Center at no additional cost. It provides immutable point-in-time snapshots that help reduce Recovery Time Objective (RTO) in the event of ransomware or accidental deletion without requiring a full backup restore cycle.

How much RAM does the DS1520+ ship with, and is it upgradeable?

The DS1520+ ships with 8GB DDR4. Synology supports RAM upgrades on this unit — check Synology's compatibility list for validated modules before purchasing, as using unvalidated memory can cause instability.