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Synology DiskStation DS420j Review

by Adam Armstrong
Synology DiskStation DS420j

The Synology DiskStation DS420j is a 4-bay NAS that is aimed for home or home office use. The DS420j is an ideal choice for a home or small office looking to set up a private cloud. This cloud allows for cross-platform file sharing or an easy way to backup data. Powered by Synology’s award-winning DiskStation Manger (DSM), the NAS, like all their devices, come with several powerful tools.

The Synology DiskStation DS420j is a 4-bay NAS that is aimed for home or home office use. The DS420j is an ideal choice for a home or small office looking to set up a private cloud. This cloud allows for cross-platform file sharing or an easy way to backup data. Powered by Synology’s award-winning DiskStation Manger (DSM), the NAS, like all their devices, come with several powerful tools.

Synology DiskStation DS420j

While the DS420j is a compact little NAS, it does have the ability to store over 60TB of data. Supporting up to 16TB HDDs, users can hit 64TB in the four drive bays. The NAS leverages a Realtek RTD1296 4-core 1.4 GHz CPU, 1GB of DDR4 RAM, and supports various networking protocols through its 1GbE port. Synology claims the DS420j can hit over 112MB/s sequential reading and writing throughput while encrypted. The NAS sports an environmentally friendly design, using only 7.88W in hibernation mode.

We did a video overview here:

The Synology DiskStation DS420j comes with a 2-year limited warranty and can be picked up for $300.

Synology DiskStation DS420j Specifications

CPU Model Realtek RTD1296
CPU Architecture 64-bit
CPU Frequency Quad Core 1.4 GHz
Hardware Encryption Engine Yes
System Memory 1 GB DDR4
Drive Bays 4
Compatible Drive Type 3.5″ SATA HDD
Maximum Internal Raw Capacity 64 TB (16 TB drive x 4) (Capacity may vary by RAID types)
Maximum Single Volume Size 108 TB
Hot Swappable Drive Yes
External Ports
RJ-45 1GbE LAN Port 1
USB 3.0 Port 2
File System
Internal Drives EXT4
External Drives EXT4
Size (Height x Width x Depth) 184 mm x 168 mm x 230 mm
Weight 2.21 kg
System Fan 80 mm x 80 mm x 2 pcs
Power Supply Unit / Adapter 90W
AC Input Power Voltage 100 V to 240 V AC
Power Frequency 50/60 Hz, Single Phase
Power Consumption 21.71 W (Access)

7.88 W (HDD Hibernation)

British Thermal Unit 74.08 BTU/hr (Access)
26.89 BTU/hr (HDD Hibernation)
Operating Temperature 0°C to 40°C (32°F to 104°F)
Storage Temperature -20°C to 60°C (-5°F to 140°F)
Relative Humidity 5% to 95% RH
Warranty 2 Years

Design and Build

The Synology DiskStation DS420j is a 4-bay tower NAS that is small enough to fit on a desktop. Along the front of the device is ventilation as well as the power button and LED indicators. From left to right the LED indicators are Status, LAN, and four Disk indicators.

Synology DiskStation DS420j Front

Flipping the device around, fans take up the most real estate. At the top right is a Kensington security slot. Along the bottom is a power port, a LAN port, two USB 3.0 ports, and a reset button.

Synology DiskStation DS420j Rear

Synology DiskStation DS420j Performance

Review Configuration

For our testing, we configured the Synology DiskStation in RAID1 using two Seagate IronWolf 16TB HDDs. Each disk configuration used EXT4 volumes and measured iSCSI and CIFS performance across one 1GbE LAN connection.

Enterprise Synthetic Workload Analysis

Our enterprise shared storage and hard drive benchmark process preconditions each drive into steady-state with the same workload the device will be tested with under a heavy load of 16 threads with an outstanding queue of 16 per thread, and then tested in set intervals in multiple thread/queue depth profiles to show performance under light and heavy usage. Since NAS solutions reach their rated performance level very quickly, we only graph out the main sections of each test.

Preconditioning and Primary Steady-State Tests:

  • Throughput (Read+Write IOPS Aggregate)
  • Average Latency (Read+Write Latency Averaged Together)
  • Max Latency (Peak Read or Write Latency)
  • Latency Standard Deviation (Read+Write Standard Deviation Averaged Together)

Our Enterprise Synthetic Workload Analysis includes four profiles based on real-world tasks. These profiles have been developed to make it easier to compare to our past benchmarks as well as widely-published values such as max 4k read and write speed and 8k 70/30, which is commonly used for enterprise drives.

  • 4K
    • 100% Read or 100% Write
    • 100% 4K
  • 8K 70/30
    • 70% Read, 30% Write
    • 100% 8K
  • 8K (Sequential)
    • 100% Read or 100% Write
    • 100% 8K
  • 128K (Sequential)
    • 100% Read or 100% Write
    • 100% 128K

In the first of our enterprise workloads, we measured a long sample of random 4K performance with 100% write and 100% read activity. Looking at read IOPS, the Synology DiskStation DS420j was able to hit 1,108 IOPS in iSCSI and 156 in CIFS. For write, we saw 781 IOPS iSCSI and 751 IOPS in CIFS.

Next up 4K average latency. Here the DS420j had read latency of 230.9ms iSCSI and 1,629.2ms CIFS. For write latency, we saw 327.4ms iSCSI and 340.4ms CIFS.

Next up 4K maximum latency. The NAS had read scores of 687.6ms iSCSI and 3,243ms CIFS. With write latency we saw 2,267.8ms iSCSI and 1,929ms in CIFS.

Our final 4K test is standard deviation where we saw read latency of 135ms in iSCSI and 89.9ms in CIFS. For write we saw 402.3ms iSCSI and 193ms CIFS.

Our next benchmark measures 100% 8K sequential throughput with a 16T16Q load in 100% read and 100% write operations. Here, the DS420j had strong iSCSI scores of 14,286 IOPS read and 14,288 IOPS write. For CIFS, the NAS had 14,183 IOPS read and 11,301 IOPS write.

Compared to the fixed 16 thread, 16 queue max workload we performed in the 100% 4K write test, our mixed workload profiles scale the performance across a wide range of thread/queue combinations. In these tests, we span workload intensity from 2 threads and 2 queue up to 16 threads and 16 queue. In throughput, the Synology DS420j saw highs of 821 IOPS iSCSI and 196 IOPS CIFS.

iSCSI continued to perform better in our 8K 70/30 average latency with an ending score of 311.2ms compared to the CIFS 1,299.3ms.

For 8K 70/30 max latency the CIFS configuration was slightly better with 4,113.9ms versus the iSCSI 4,239.6ms.

In 8K 70/30 standard deviation iSCSI edged ahead with 396.1ms compared to CIFS 417.1ms.

The last Enterprise Synthetic Workload benchmark is our 128K test, which is a large-block sequential test that shows the highest sequential transfer speed for a device. In this workload scenario, the iSCSI configuration saw 115.7MB/s read and 115.6MB/s write. CIFS had 115.7MB/s read and 114.9MB/s write.

Synology DS420j 128K


The Synology DiskStation DS420j is a home, small office NAS with enough capacity and performance for those use cases. The 4-bay NAS has a maximum capacity of 64TB, leveraging four 16TB HDDs. It is great for creating a private cloud and sharing files on any device that can connect to it. Through DSM, users can setup other abilities such as creating a surveillance solution supporting up to 16 IP cameras. DSM has several features making it good for a backup and sync solution as well.

Looking at performance, we looked at RAID1 configuration with both iSCSI and CIFS. iSCSI tended to be the higher performer, which isn’t unusual. In our 4K tests we saw read scores of 1,108 IOPS, 230.9ms average latency, 687.6ms max latency, and 135ms standard deviation for iSCSI. For CIFS read in 4K we saw 156 IOPS, 1,629.2ms average latency, 3,243ms max latency, and 89.9ms in standard deviation. With 4K write iSCSI gave us 781 IOPS, 327.4ms averaging latency, 2,267.8ms max latency, and 402.3ms standard deviation. CIFS 4K write scores were 751 IOPS, 340.4ms average latency, 1,929ms max latency, and 193ms standard deviation. For 100% 8K sequential throughput the DS420j scores of 14,286 IOPS read and 14,288 IOPS write for iSCSI and 14,183 IOPS read and 11,301 IOPS write for CIFS. With a 128K large-block sequential test, we saw speeds of 115.7MB/s read and 115.6MB/s write iSCSI and 115.7MB/s read and 114.9MB/s write CIFS.

At an affordable price, the Synology DiskStation DS420j can add shared storage to any home, offering the benefits of backing up media from desktops, notebooks or phones. DSM gives users tons of cloud-connected features, allowing the small NAS to be leveraged well even in smaller office environments as well.

Synology DiskStation DS420j on Amazon

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