The Synology DS1621+ is a worthy upgrade to the DS1618+, which is still an excellent NAS server today. That's to say, in many ways, the new server brings excellence to a new level.
No, it's still not perfect. But if you're looking to get the most out of a network-attached storage solution for a demanding home or even a small business, the DS1621+ is an easy recommendation.
The server is worth every penny of its $800 price tag (diskless). And for this review, I went (almost) all out and invested a lot more than that. In the end, most of that proved to be money well spent.
Synology DS1621+: The powerful AMD-based upgrade to the DS1618+
The DS1621+ is the immediate upgrade to the DS1618+ that came out in 2018. There was no 6-bay DiskStation Plus server in between the two.
(Per Synology's naming convention, the DS1621+ is of the 2021 model year. However, it was first released in late 2020.)
And the two are very similar. In fact, Synology servers are generally conforming and consistent -- a later model year is an incremental improvement of the previous one.
That said, the DS1621+ has everything the DS1618+ has plus some extras and differences, including:
- Built-in NVMe M.2 slots for cache storage. Previously you must use a PCIe add-on adapter for the caching option with the DS1618+.
- The new server now uses a more powerful AMD processor.
- ECC RAM is now a requirement. ECC generally means more stable performance.
And here's the most interesting part: The new servers come with a lower price tag at launch, which is $100 less than the DS1618+ at its time.
Familiar 6-bay design
Design-wise, the DS1621+ is almost identical to the previous model. It's a 6-bay server with the ability to host two expansion units to house up to 16 internal drives. Out of the box, it can handle six. Considering you can get hard drives of significantly more than 10TB each, six drives are plenty in terms of storage.
If you want to use standard 3.5-inch hard drives, the server is completely tool-free. You can install or remove each drive with your bare hands. If you want to use 2.5-inch drives (HDDs or SSDs), though, you'll need to screw them on their drive tray, and there are more than enough screws included in the box.
On the back, the server comes with the same amount of ports as its predecessor, including four Gigabit LAN ports, two USB 3.0 ports, and two eSATA ports (to host expansion units).
Unfortunately, there's no Multi-Gigi port, either. For that, you'll need to resort to the server's PCIe add-on slot. This slot can work with all Synology 10Gbps adapter cards, including the Dual-SFP+ E10G17-F2 and the Dual-BASET E10G18-T2. I tried both out for my testing, and they worked equally well.
The DS1621+ comes included with a 4GB random access memory (RAM) stick installed on one of its two memory slots on its underside.
Truth be told, the stock 4GB is enough for most cases -- I used the DS1618+ for years with just that. However, upgrading the RAM is necessary if you intend to run lots of applications or multiple virtual machines.
Notes on the Synology DS1621+’s RAM upgrade
Per Synology, you can upgrade the server up to 32GB (2x 16B) of RAM. That's likely because the company only sells 16GB and lower-capacity sticks. Since the server runs 64-bit Linux, I don't see why it couldn't handle more than 32GB. But 32GB is plenty compared to the original 4GB, and I haven't tried more than that.
In any case, keep the following in mind when it comes to memory upgrades:
- It's best to use RAM approved by Synology. (Which is very expensive, unfortunately.)
- You can use certain third-party RAM if you want to take the risk. In this case, the server will give you an "unsupported" memory warning, which you can turn off in the Control Panel's notification area.
- It's OK to use two sticks of different sizes (like 4GB and 8GB). Generally, in the server world, there's no benefit in using two identical sticks. In my case, I tried the server out with 4GB and 16GB sticks.
- The DS1621+ won't work with the DS1618+'s stock RAM (it's a non-ECC). So in an upgrade, you can't move the old RAM over. However, the other way around is possible. The DS1618+ will take the RAM used for the DS1621+, but only if you have removed its stock non-ECC stick.
Finally, the DS1621+'s two NVMe M.2 slots are hidden inside the server on its left inner wall. To get to them, you will need to remove a few drive trays from 1 to 4. Nonetheless, you can easily install or remove the SSD with your bare hands.
Notes on using cache on Synology DS1621+
While the M.2 slots' availability is a welcome change, their use only applies to applications that require fast random access performance. Examples of these applications include database access, video/audio editing, webpage serving, etc.
SSD caching is not necessary for sequential (file copy) performance. In fact, using a cache, in this case, might adversely affect the throughput speeds, as you'll note in the performance section below.
Also, SSD caching should be used only with a hard-drive-based volume. If you use SSD as storage, caching is completely unnecessary.
Finally, the M.2 slots can only be used for caching. They will not work to host a regular data volume. (Hopefully, this will change in the future.)
Hardware specifications: DS1621+ vs. DS1618+
Again, out of the box, like the case of the DS1618+, the new DS1621+ can handle up to six internal drives. If that's not enough, you can add another ten via two DX517 expansion units.
|CPU||AMD Ryzen V1500B|
quad-core 2.2 GHz
|Intel Atom C3538 |
|System Memory||4GB ECC DDR4||4GB Non-ECC DDR4|
|Max Memory||32 GB via two memory slots |
(16 GB x 2)
|32 GB via two memory slots |
(16 GB x 2)
|Dimensions||6.53 x 11.1 x 9.57 in |
(166 x 282 x 243 mm)
|6.53 x 11.1 x 9.57 in |
(166 x 282 x 243 mm)
|Weight||11.24 lbs (5.1 kg)||11.24 lbs (5.1 kg)|
|Expansion Support||Yes (two units)||Yes (two units)|
|Drive Interface||SATA 6Gbps/3Gbps; |
|SATA 6Gbps/3Gbps; |
|Maximum Raw Capacity||96 TB (6x16TB Drives)||96 TB (6x16TB Drives)|
|Built-in M.2 Slots||Two||None|
|RAID Types||SHR, Basic, JBOD, RAID 0, RAID 1, |
RAID 5, RAID 6, RAID 10
|SHR, Basic, JBOD, RAID 0, RAID 1, |
RAID 5, RAID 6, RAID 10
|Ports / Interfaces||4x RJ-45 1GbE LAN, |
3x USB 3.0, 2x eSATA
|4x RJ-45 1GbE LAN, |
3x USB 3.0, 2x eSATA
|PCIe Expansion||1x Gen 3 x8 PCIe slot||1x Gen 3 x8 PCIe slot|
|Add-in-card Support (not included)||10GbE Network Interface Cards |
(E10G18-T2 / T1, or E10G17-F2)
|Dual SATA M.2 SSD adapter (cache); |
Or 10Gbe NIC Card
|Operating System||DSM 6.x (and later)||DSM 6.x (and later)|
|File System (Internal / External)||Btrfs, EXT4 / Btrfs, EXT4, EXT3, |
FAT, NTFS, HFS+, exFAT (via app)
|Btrfs, EXT4 / Btrfs, EXT4, EXT3, |
FAT, NTFS, HFS+, exFAT (via app)
|Warranty||3 years||3 years|
The full hardware specifications of the DS1621+ can be found here.
An easy upgrade
For those thinking of migrating from the DS1618+ to the DS1621+, here's some good news. It's super easy.
Despite using completely different processors (AMD vs. Intel), you can migrate the two's storage with ease. And the fact they use the same drive trays helps, too.
In my case, all I had to do was take the old server's preoccupied trays and insert them into the new server in the same order.
After that, turn the new server on, run Synology Assistant from a connected computer, and follow the on-screen instruction to migrate. Shortly after, my new server was up and running with all the old data and settings.
You can also upgrade from most DiskStation servers to the DS1621+. Just make sure your old server has six or fewer internal drives.
Note on surveillance station in an upgrade
If you have bought extra camera licenses for the old server and want to use them with a new server, make sure you remove them from the old server before migrating the storage.
Like all Synology DiskStation servers, the DS1621+ includes just two camera licenses. That's quite a shame considering it'll make an excellent Surveillance system.
Synology DS1621+: Detail photos
The state-of-the-art operating system and high-quality apps galore
Like the case of all other DiskStation servers, the DS1621+ runs DiskStation Manager (DSM) operating system, which is by far the best for NAS servers. The server comes with DSM 6.0 and will support DSM 7.0, which is currently available as a beta.
As a result, if you have used a Synology server before, you'll feel right at home with the DS1621+. The experience is conforming and persistent. For that reason, to avoid repeating myself, I detailed that in this separate frequently updated post on Synology servers.
However, I want to add one thing about the DS1621+, which is the support for virtual machines.
While you can run VM Manager on all Plus servers, the DS1621+'s AMD Ryzen CPU makes VMs a much better experience. Specifically, my Windows 10 virtual machine now performed close to that of a regular computer.
Synology DS1621+: Excellent performance
I tested the DS1621+'s data copy speeds using a 10Gbps connection via adapter cards, two 2TB WD RED SA500 SSDs (in SHR RAID, which is similar to RAID 1), and three 10GB Seagate Ironwolf NAS hard drives (in SHR RAID, which is similar to RAID5).
To make the result more meaningful and comparable, I retested the DS1618+ with the same storage volumes mentioned above and tested both servers without SSD caching and their 4GB stock RAM.
And the new DS1621+ server proved to be an excellent upgrade in copy performance alone, as you can see in the chart below.
Additionally, just for kicks, I added two Seagate NAS SSDs as cache and attached them to the HDD-based volume. As expected, the copy speeds of this volume were now slightly slower.
Specifically, via and 10Gbps connection, this volume delivered the sustained speeds of 348.37MB/s (read) / 330.36MB/s (write) and 350.60MB/s (read) / 353.79MB/s (write) with and without cache, respectively. Again, caching is really unnecessary when you need to transfer a lot of data.
But chances are you use the NAS server for a lot more than just raw file storage. In that case, and only then, it's a good idea to invest in a couple of NVMe SSDs.
For this review, I used the DS1621+ for more than a month. During this time, it proved to be a much better solution with my extra upgrades, namely the SSD storage and additional 16GB of RAM. At stock configuration, though, it'd likely be very similar to the DS1618+.
That said, I'm now happy to use it as my main server. And considering how the DS1618+ has worked in the past almost three years -- and it's still working very well now --, I have no doubt the DS1621+ will last.
Synology DiskStation DS1621+'s Rating
Powerful AMD CPU delivers fast and reliable performance
Robust DiskStation Operating System with tons of useful home and business applications, including Virtual Machines
Straightforward and consistent setup, upgrade, and management
Built-in M.2 NVMe slots
Lots of network storage options
Expensive RAM upgrade
No built-in 10Gbps port (adapter required)
Only two camera licenses included
Again, the Synology DS1621+ is an excellent NAS server. The included six drive bays are a good number for those wanting to use multiple storage volumes. And the new powerful AMD CPU opens up a lot of potential, especially in terms of virtualization.
The DS1821+ is virtually the same but with two additional drive bays.
That said, get one today and invest in some SSD storage and extra RAM, and you'll have yourself the ultimate NAS server that delivers in all aspects of home networking and storage. And the effective implementation of virtual machines means small businesses won't miss out either. I recommend it!