Synology DS420j mini review



The DS420j is one of my more boring tech purchases. It does exactly the same stuff as my old DS411j from nine years ago. But has enough CPU and memory to do it with ease rather than being stretched to the limit.


I bought a Synology DS411j Network Attached Storage (NAS) box in late Apr 2011, and at the time remarked that it was ‘a great little appliance – small, quiet, frugal, and fast enough’.

Over time fast enough became not quite fast enough, though the issue was more with the limited 128MB of memory rather than the Marvell Kirkwood 88F6281 ARM system on chip (SOC). As successive upgrades to DiskStation Manager (DSM) came along I found myself firstly pairing back unnecessary packages, and then just putting up with lacklustre performance due to high CPU load (due to too little free RAM).

Having everybody at home for lockdown over the past few weeks hasn’t been easy on the NAS, with all of us hitting it at once for different stuff, so it was definitely creaking under the load. I bought a DS420j from Box for £273.99 (+ £4.95 P&P because I wanted it before the weekend rather than waiting for free delivery)[1].

The new box

Is black, and has the LEDs in different places. This is of no consequence to me whatsoever, as the NAS lives on a shelf in my coat cupboard where I never see it.

It uses the same drive caddies as before, the same power supply, and has the same network and USB connectivity.

The differences come with the new 4 core SOC, a Realtek RTD1296, which provides more than 4x the previous CPU performance, and 1GB DDR4 RAM, which is 8x more, and a bit faster.


Moving 12TB of storage, including everything that the family has accumulated in over 20 years is not for the faint-hearted. Thankfully Synology makes it really easy, and has a well documented process.

I’d already taken a config backup and ensured I was on latest DSM before the new NAS arrived, so when I was ready to switch it was simply a matter of:

  1. Powering down and unplugging the DS411j.
  2. Switching the disk caddies to the DS420j (they’re the same, so fitted perfectly).
  3. Plugging in the DS420j and powering up.
  4. Selecting the migration option and clicking through to DSM upgrade.
  5. Waiting for the system to come back up and restoring the config.
  6. Another restart.
  7. Altering the DHCP assignment in my router so that the new NAS would have the IP of the old NAS, then switching between manual IP and auto IP in DSM so that the new IP is picked up.
  8. Upgrading the installed packages (for new binaries?).
  9. Re-installling Entware opkg (so that I can use tools like GNU Screen).

The entire process took a few minutes, and then everything was back online.


Using the new NAS is noticeably snappier than before, and when I run top the load averages I’m seeing are more like 0.11 and 11.0.

Everything else is the same as before, but I couldn’t really expect more, as I was already running the latest DSM. I don’t ask much of my NAS – share files over CIFS and NFS, back stuff up to S3, run some scripts to SCP stuff from my VPSs, that’s it.

I think I have a few more options now for upgrading the disks as I run out of space, but I have a TB or so to go before I worry too much about that.


This is probably one of the most boring tech purchases I’ve made in ages. But storage isn’t supposed to be exciting, and I’m glad Synology make it so easy to upgrade from their older kit.

Here’s hoping that this one lasts 9 years (or longer). It’s just a shame that the cost of storage TB/£ has remained stubbornly flat since 2011. The next spindles upgrade is going to be $EXPENSIVE.


[1] and I now see it for £261.99 so my timing was bad :/

7 Responses to “Synology DS420j mini review”

  1. 1 andyjpb

    I assume it has a single GigE for IO?

    Is it able to saturate that with your normal file access patterns?

    • According to the official benchmarks it’s nowhere near fast enough to saturate that GigE port

      • 3 andyjpb

        Ah, that’s a shame.
        I think the Microservers can. Is there a big difference in power consumption between the Synology and your Microservers or is the bulk of it all drawn by the disks themselves?

        I suppose that if most of the clients are on WiFi then you only need a few hundred Mbps to fill the bottleneck.

      • 4 andyjpb

        On closer inspection, those graphs seem to be in MB/s but the interface is 1Gbps so something’s up… The blurb at the bottom of the page doesn’t explicitly specify whether they’re doing an end-to-end test or whether they’re looking at local disk bandwidth on the NAS.

        So the DS420j is either filling 1/10 of the 1Gbps port or just about all of it and the other units are overspec’d for that interface (and hold their own in the later tests with faster interfaces).

      • I’m seeing practical throughput at 43MB/s copying big files from the NAS to my desktop. So bandwidth isn’t the bottleneck (as I can get 940 Mb/s on iperf). Maybe if I had SSDs in the NAS (and didn’t care about redundancy) the bottleneck could be moved to the NIC, but with my RAID of HDDs it’s elsewhere.

  2. 6 mgnelsonwp

    Enable Jumbo frames yet? Was a big boost on my QNAP.

  3. More comments on the LinkedIn thread

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