Synology DS420j full review

The modern NAS drive has become a popular option for many homes, providing a convenient location to backup files from multiple devices and share them with others. Most start with a single or dual-drive system, and for those that grow large media collections, the next logical step is a four-drive solution like the Synology DS420j system that we’ve tested here.

The extra drives allow for greater overall capacity, more resilience against drive failure and less chance of data loss. As a J Series machine, the DS420j is aimed at those that want those good things, but at an affordable price.

But how does the DS420j stack up against the DS418j it replaces, and other similarly specified NAS options?


The UK price MSRP for the DS420j is £231.4 (260 Euros) exclusive of VAT, or £277.68 inclusive of tax. You can buy the DS420j from the likes of Amazon and eBuyer.

In the US it's available from Amazon for $299.

The QNAP equivalent is the TS-328 and it costs around £190/$240. It uses the same CPU, has 2GB of RAM (not 1GB), and it also includes an extra USB port, and dual Ethernet ports.

Around the same price is the Netgear ReadyNAS RN214. It also features a quad-core CPU, has 2GB of RAM and three USB ports.

We should also mention its predecessor, the DS418j that can be bought for around £300 in the UK and can be found for $369 on in the US. With the new design launched, we’d expect the DS418j to become cheaper in the coming months, but for now the 420 is actually cheaper.

Check our chart of the best NAS drives to see what other options you have.

Design & Build

The best way to consider the design of the Synology DS420j is the adage about why you might want to fix something that isn’t broke.

And, that’s precisely the view taken by Synology, as the enclosure that the DS420j uses is practically identical to the one that the DS418j came in, and the DS414j before that. In our office, we still have, and use a nine-year-old DS411 machine that’s very similar.

When a design has been used for such a long time then it clearly has merit and therefore the reliability of this equipment is clearly going to be better because it uses a tried and tested format.

The only weakness of the design, addressed by the newer enclosure used in the DS418, is that while flashing LEDs on the front would indicate a drive number that might have failed, how that relates to the internal trays at the back isn’t obvious.

The lights are mounted horizontally and the drives stacked vertically so unless you refer to the documentation, you won’t realise that drive one is at the top, not the bottom, and you could easily pull the wrong drive out.

Synology DS420j review

Putting aside that potential catch, this is a NAS design that has been widely copied by other makers due to the simplicity of the construction and assembly. The front and floor are plastic, the top, sides and rear are all thin pressed sheet metal. There are two 80mm fans are the rear to eject heat and plenty of slots for cool air to enter for that airflow to work.

All the ports are at the back and the PSU is an external laptop-style block that doesn’t contribute extra heat internally and can easily supply the relatively small amount of power that the system uses even when fully occupied with hard drives.

The currently quoted maximum raw capacity is 64TB should you be willing to invest the roughly £1,800/$1,800 on storage needed to populate it with four 16TB drives.

It isn’t a necessity to fill all four bays, although if you want a resilient system, you need at least two drives of the same capacity. Synology DSM can expand the defined volumes should you add more drives, and you can even sequentially swap out drives of larger capacity if you are prepared to let the system reorganise between each drive swap.

And, for those that want a fresh start, it is possible to secure the contents to external storage, make major changes to the drive layout and then move the data back. The elegance of this honed hardware solution combined with the maturity of the DSM operating system is a major factor in why Synology is the market leader in home NAS solutions.

Specs & Features

Before we dive into the details, it’s worth trying to understand Synology and why the DS420j isn’t a technical revolution from the DS418j that it replaces from 2018.

When Synology introduces new models, it creates a problem for older hardware still in the channel, as the newer designs have better features.

Synology has struggled with this issue for years, and the DS420j is a classic example of its difficulty in not undermining existing products. Because while it wants to make the DS420j better than the DS418j that came before, it can’t make it better than the flagship DS418 it still sells.

That leaves a very narrow scope for enhancing the DS420j and making the difference between this NAS drive and the one it replaces remarkably subtle.

Synology DS420j software interface

Reading the specifications of these two machines finding any difference is something of a challenge. It uses the same enclosure and the same power supply as before. And, it can take the same number of drives, of the same size, and has the same USB port layout and LAN capability.

The only major difference between the DS420j and the DS418j is the central ARM processor. The previous model uses the Realtek dual-core RTD1293, and the DS420j has the better Realtek RTD1296, a quad-core design with the same 1.4GHz clock speed.

Those familiar with the various chips used on Synology NAS will realise it is identical to the previous DS418 model, so the new the DS420j is essentially the old DS418, but with only 1GB of DDR4, not 2GB. It is still possible to buy the more expensive DS418 to get double the RAM and a newly redesigned enclosure. Or you can get the DS418j for a little less and live with a dual-core platform.

For those curious, the memory is soldered directly on to the board, so you can’t upgrade the DS420j and turn it into a full DS418 spec box, sadly.

Synology DS420j apps

If the Realtek RTD1296 and 1GB of RAM is enough for your plans, then the DS420j is the right platform for you, but those than need more power should seriously consider the DS918+, as it has the Intel Celeron J3455 CPU, but it also has 4GB of RAM, upgradable to 8GB, hardware transcoding and it can also take an external drive box to expand the array to nine drives.

Normally in a Synology review, we’d talk about the incredible number of applications supported by the DSM operating system, but in this case, they’re the same apps that the DS418j supports. These are wonderful apps, do all the things that most home users would want from a NAS, but the DS420j doesn’t have access to any that the DS418j wouldn’t run.


As we might have hinted already, this isn’t an obvious choice where the new equipment is clearly superior to the old.

Synology has dug itself a specifications hole where the changes between models are now so slight that most people wouldn’t notice the difference purely on user experience. In short, the newer machine runs the same apps as before, at the same speed and using the same DSM operating system.

If you intend to use many apps simultaneously on the NAS, then the extra CPU cores might be helpful, but as it doesn’t have any additional RAM, you’d probably be better off buying the DS418 and getting the extra memory that comes with that design.

For those who primarily use the file server functionality, the old DS418j will do the job just as well, and depreciation should make it cheaper by the summer. However, if you want a system now, the DS420j is easily worth the asking price.

Synology has built a NAS solution that functions brilliantly on all the hardware in its NAS stables and swapping out a dual-core CPU one for a quad-core design doesn’t open any dramatically different opportunities without any extra RAM.

The DS420j is an excellent choice as a four drive NAS, and competitively priced, but it isn’t a vast improvement over the machine it replaces.


Synology DS420j: Specs

  • Processor: Realtek RTD1296 4-core 1.4 GHz
  • Memory: 1 GB DDR4
  • Drives: 4 x 3.5in or 2.5in SATA HDD/SSD (drives not included)
  • Raid Modes: Synology Hybrid RAID (SHR), Basic, JBOD, RAID 0, RAID 1, RAID 5, RAID 6, RAID 10
  • Networking: 1x 1GbE LAN port
  • Networking Protocols: SMB, AFP, NFS, FTP, WebDAV, CalDAV, iSCSI, Telnet, SSH, SNMP, VPN (PPTP, OpenVPN, L2TP)
  • USB ports: 2x USB 3.0 Type A
  • OS: Synology DSM 6.2.2
  • OS Languages: English, German, French, Spanish, Italian, Magyar, Chinese, Japanese, Korean, Portuguese, Polish, Norwegian, Swedish, Danish, Turkish and Czech
  • Maximum capacity: 64TB (4x 16TB)
  • Maximum Single Volume: 108TB
  • Internal drive formats: ext4
  • External drive formats: ext4, ext3, FAT, NTFS, HFS+(read only), exFAT
  • Size (HxWxD): 184 x 168 x 230mm

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