Synology DS1525+ Review: A Solid and Pricey Multi-Gig NAS Server

The Synology DiskStation DS1525+ network-attached storage (NAS) server, first available in the US on June 25, 2025, is arguably the best among Synology’s new and controversial 2025 releases.

The contentious storage requirement aside, it’s the only one among its peers that’s truly an upgrade. It has everything of the previous model, the DS1522+, and then some.

Here’s the bottom line: If you can stomach Synology’s storage requirements, the DS1525+ is an excellent NAS server to buy today, worth its $799.99 retail price (diskless). This five-bay server will make it worth the extra total cost of ownership compared to the slightly lesser previous model. However, if you already have the DS1522+, which is excellent in its own right, there’s no need to rush to upgrade, especially if you already added 10Gbps to it.

Dong’s note: I first published this post as a preview on Jun 25, 2025, when the DS1525+ was announced, and updated it to an in-depth review on July 15, 2025, after thorough hands-on testing.

Synology DS1525+: Dual 2.5GbE ports with 10GbE upgrade option

The first thing to note about the DS1525+ is that, like all 2025 Plus models, it comes with Synology’s new storage requirement: it won’t work with third-party drives that are not on the approved list. To put it bluntly, you’ll generally have to get Synology-branded hard drives and SSDs before you can make use of your new server.

With that out of the way, the new server’s name means it features five native drive bays to accommodate up to five internal drives, as well as the option to host two expansion units, allowing for a total of 10 additional drives. In all, it can handle a few hundred terabytes of storage space when fully loaded.

Similar to the previously announced DS925+, the DS1525+ also utilizes a USB-C port for storage expansion and requires the new DX525. Its USB-C expansion ports feature USB 3.2 Gen 1 (a.k.a. USB 3.0), which caps at 5Gbps. It’s a bit disappointing that Synology doesn’t use Thunderbolt or a faster USB grade for them.

In terms of network connectivity, the DS1525+ represents a significant upgrade from its predecessor. It forgoes Gigabit entirely and instead comes with two 2.5GbE ports. You can even use these two ports in a link aggregation setup to create a 5Gbps bonded link. Additionally, like the case of the DS1522+, it also features a Network Upgrade slot that can accommodate a Synology E10G22-T1-Mini module, quickly adding 10Gbps capability.

Physically, the new server retains the design that’s been consistent in all previous DS15xx+ servers. The table below illustrates the evolution of this lineup over the years since the first DS1511+ was released in 2011.

Synology DS15xx+ servers: Hardware specifications

	DS1525+	DS1522+	DS1520+	DS1517+	DS1515+	DS1513+	DS1511+
Model Year	2025	2022	2020	2017	2015	2013	2011
Gigabit Port	none	4
Multi-Gig Port	2x 2.5GbE	None
Dimensions	16.6 x 23 x 22.3 cm
Weight	2.67 kg
USB Port	2x USB 3.0	2x USB 3.0	2x USB 3.0	4x USB 3.0	4x USB 3.0	2x USB 3.0, 4x USB 2.0	4x USB 2.0
Expansion Port	2x USB-C (USB 3.0)	2x eSATA
CPU	2.2 GHz AMD Ryzen V1500B Quad-core (8 Threads)	2.6 GHz AMD Ryzen R1600 Dual-Core (4 Threads)	2.0GHz Intel Celeron J4125 Quad-Core	2.4 GHz Intel Atom C2538 Quad-Core	2.4 GHz Intel Atom C2538 Quad-Core	2.13 GHz Intel Atom Dual Core	1.8GHz Intel Daul-Core
RAM	8GB (Expandable to 32GB)		8GB (Expandable to 20GB)	2GB (Expandable to 16GB)		2GB (Expandable to 4GB)	1GB (Expandable to 3GB)
Built-in NVMe M.2 slot	2 (caching or storage)			None
PCIe slot (upgrade)	None			1x 8-lane PCIe slot	None
Upgrade Options	Synology E10G22-T1-Mini (1x 10Gbps BASE-T)		None	Synology E10G21-F2 (2x SFP+ port) Synology E10G18-T1 (1x 10Gbps BASE-T) Synology E10M20-T1 (1x 10Gbps BASE-T, 2x NVMe M.2 slot)	None

DS1525+ vs DS1522+: Tip on which to consider

As shown above, the DS1525+ has a minor upgrade in processing power compared to the DS1522+. It features an older but more powerful CPU.

However, the new server has a significant upgrade in terms of connectivity compared to its predecessor. The two 2.5 Gbps network ports yield much higher performance right out of the box.

If you give both servers the 10GbE upgrade, though, both have similar network performance. The DS1525+ managed to edge out a little bit in my real-world trial, though that might just be because it was tested with the latest DSM version.

The point is that the DS1525+ has enough to qualify as an upgrade to the previous model—it’s the same or “better” in all aspects. Still, whether it has enough to compensate for Synology’s new storage policy, which makes it a more expensive server to get up and running, remains a good question.

A familiar five-bay Synology experience

Besides the hardware specifications and the new drive requirements, running DSM 7, the DS1525+ offers a familiar NAS experience similar to that of the DS1522+ and any other existing Synology servers released in the past 10 years. You can expect advanced features and functionalities via different software packages or apps.

In my experience, five is the optimal number of drive bays among Plus servers, as it provides users with all possible RAID configurations and sufficient storage space, thereby minimizing the need for an expansion unit.

I’ve never tested any Synology server with an expansion unit. However, considering the single USB 3.0 connection, adding an expansion unit will likely compromise the server’s performance. That said, it’s best to get a server with even more native drive bays, such as the DS1825+, or use hard drives of higher capacities instead.

Synology DS1525+: Excellent overall performance at a price

I tested the Synology DS1525+ for over a week, and it worked well. However, before that, let’s run through the cost of the hardware I used.

Unlike all previous servers, this time I used exclusively Synology hardware, including five 4TB HAT3300 HDDs, two 480GB SAT5221 SATA SSDs, and two 400 GB SNV3410 SSDs. Additionally, I also used an E10G22-T1-Mini 10Gbps upgrade module. If you’d like to purchase the same items on Amazon, here’s the list.

You may have noticed that I used drives of relatively modest capacities, yet the total cost is still close to $1,300. For testing, I used a few more drives than necessary, but the idea is that you need to spend a substantial amount, besides the cost of the server itself, before you can get this server up and running at its bare minimum. Most importantly, you would save between 25% and 60% of the cost if you could use third-party options, especially if you opt for SSDs.

It’s worth noting that, despite the high cost, Synology-branded drives are relatively dated. The SNV3410, for example, still uses the PCIe Gen 3 standard. To put things in perspective, we’ve had PCIe Gen 5 NVMe SSDs for a couple of years now.

However, using Synology hard drives has its advantages. I noted that the server was near silent. Its large ventilation fan produced a subdued humming sound, and there was no hard drive sound at all, even during heavy operation.

In terms of performance, the DS1525+ proved to be one of the fastest NAS servers I’ve tested, especially with a 10Gbps upgrade. Still, it never reached close to the top speed of a 10Gbps connection, likely due to the dated specifications of the drives mentioned above.

Conclusion

The DiskStation DS1525+ is not a must-have, but if you’re willing to live with Synology’s new storage lock-in policy, it’s the only among the new 2025 Plus (+) servers that’s worth buying over the previous model it replaces. The new server is a solid multi-Gig upgrade over the DS1522+ with matching real-world performance. Consider it today!