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Synology DiskStation DS720+ and DS420+Review

Synology traditionally operates a two-year refresh cycle for most of its NAS appliances and has recently announced a slew of new desktop models. In this review we look at the latest DS720+ and DS420+ and put them both through their paces in the lab to help you make the right buying decision.

The DS720+ is clearly a straight replacement for the DS718+ whereas the DS420+ looks more closely aligned with the DS418play. The last Plus model in the DS4xx family was the Atom-based DS415+ which went end of life a few years ago and the cheaper Realtek-powered Value series DS418 is still current.

At first glance, the DS720+ and DS420+ look like 2-bay and 4-bay variants of the same product family but there are a number of notable differences as they are aimed at slightly different markets. The DS720+ has a higher expansion potential as its single eSATA port supports an external 5-bay DX517 desktop unit whereas the DS420+ does not have an eSATA port so what you see is what you get.

Synology DS720+ and DS420+ rear views

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DS420+ and DS720+ Hardware features

Synology mirrored NVMe SSD cache

With a mirrored NVMe SSD cache, we saw a big boost to random IP SAN operations and reduced latency

A key feature common to both appliances is support for dual M.2 NVMe SSDs with the 2280 slots easily accessible underneath their chassis behind removable hatches. These can give a performance boost if you’re hosting demanding apps but note that the slots don’t support cheaper M.2 SATA SSDs.

The DS720+ gets the more powerful CPU as it’s endowed with a quad-core 2GHz Intel Celeron J4125 while the DS420+ has a dual-core 2GHz Celeron J4025 with both including an embedded Intel UHD Graphics 600 chip. Each appliance kicks off with 2GB of embedded DDR4 memory and the single SO-DIMM slot lurking behind their right-hand drive bay allows this to be boosted to 6GB.

Network connections are handled by a pair of standard Gigabit ports and it’s a shame Synology isn’t following the examples set by Asustor and Qnap. Upgrading these to multi-Gigabit ports would make the NVMe SSDs ideally placed to handle the higher workload demands of 2.5GbE and 5GbE connection speeds.

A single 9cms diameter fan in the DS720+ and a pair of them in the DS420+ handle all cooling and noise levels are very low making them ideal for home and small office environments. Both have dual USB 3 ports and also come with small external power adapter blocks.

DS420+ and DS720+ Performance comparisons

For performance testing, we fitted three 16TB Seagate IronWolf NAS drives in the DS420+ configured as a RAID5 array with two in the DS720+ set up as a mirror. Our test host was a Dell PowerEdge T640 tower server equipped with dual 22-core Xeon Scalable Gold 6152 CPUs, 384GB of DDR4 plus dual 10GbE ports and running Windows Server 2019.

NAS speeds over Gigabit were very similar across both appliances with Iometer reporting sequential read and write rates of 113MB/sec and 109MB/sec. However, the most noticeable differences were with CPU utilization as during the read test, the DSM Resource Monitor app reported 56% usage for the DS420+ and only 27% for the DS720+.

It was the same story for our real world copy and backup tests as although both appliances delivered the same speeds, utilization of the quad-core J4125 in the DS720+ was consistently around half that of the DS420+’s dual-core J4025. Copies to encrypted shares were handled very well with both measured at a speedy 113MB/sec but CPU utilization on the DS420+ was 36% and only 15% on the DS720+.

IP SAN speeds are good with a 500GB target mapped to our server returning sequential read and write speeds of 113MB/sec and 105MB/sec. The DS720+ handled a dual Gigabit MPIO link more efficiently with Iometer reporting read and write rates of 227MB/sec and 199MB/sec – the DS420+ returned 226MB/sec and 165MB/sec.

DS420+ and DS720+ Cache benefits

Kingston 480GB DC1000B NVMe

For testing, we chose a read/write cache and used a pair of Kingston 480GB DC1000B NVMe SSDs

To see what improvements caching would make, we installed a pair of 480GB Kingston DC1000B enterprise-class NVMe SSDs in each appliance and used the DSM Storage Manager to create a mirrored read/write cache. The results from our tests showed clearly that although no significant benefits were to be had for sequential operations, random operations improved markedly on both appliances.

With Iometer testing random read and write performance on our iSCSI MPIO target, we recorded speeds of 140MB/sec and 41MB/sec for the DS720+ while the DS420+ returned 110MB/sec and 35MB/sec. With the Kingston NVMe caches in action, these numbers rose to 226MB/sec and around 176MB/sec on both appliances.

I/O throughput also saw big improvements for our MPIO target as without the cache, Iometer reported random read and write rates for the DS720+ of 1,951 IOPS and 350 IOPS. With the cache in action, these numbers leapt up to 42,000 IOPS and 11,300 IOPS.

As expected, the DS420+ lagged slightly behind but also saw similar benefits with the non-cached MPIO target returning random read and write rates of 1,944 IOPS and 320 IOPS. Applying the cache to its volume boosted these numbers to 30,100 IOPS and 10,900 IOPS.

DSM features

Synology DSM apps

Both the DS720+ and DS420+ have access to a wealth of apps provided by Synology’s DSM

The CPUs in the DS720+ and DS420+ are both the 64-bit variety so there’s nothing on Synology’s DSM menu they can’t run. We’ve always rated DSM highly as it offers an unbeatable range of features and apps for every occasion.

The Storage Manager app provides easy access to all disk-related operations and we had no problems using it to create our NVMe SSD caches, choose read only or read/write operations and decide which volumes to apply them to. Bear in mind though, that the SSDs can only be used as caches and not to create a separate storage pool.

DSM offers a huge range of snapshot and data backup facilities with the smart Active Backup for Business (ABB) app providing backup, restore and disaster recovery services for Windows servers and workstations along with Hyper-V, VMware vCentre and ESXi hypervisors. The Drive app allows you to create your own private backup cloud as it provides Dropbox-like synchronization services for collaboration and file sharing.

Along with the Plex Media Server app, multimedia fans can play with the Video, Audio and Photo Stations with the latter including the Moments app which adds features such as image recognition techniques to sort photos into categories such as people, subjects and places. We also use the iOS Moments app on our iPad as it automatically backs up all our photos to the NAS appliance and will send new photos to it as soon as they have been snapped.

Conclusion

Both the DS720+ and DS420+ are great value and offer an impressive range of storage features with their NVMe SSD caching feature capable of making significant improvements to random operations. There are notable differences between them so which one graces your desktop or sideboard will depend on your specific requirements.

Overall, the DS720+ gets our vote for its superior range of features. Add in its greater expandability and more powerful CPU and you have a compact and highly versatile NAS appliance well suited to home and business users.

7.4Expert Score
Synology DS420+

The DS420+ is the better choice if you want the higher upfront capacity provided by its four bays. Its dual core Celeron J4025 can’t keep up with the DS720+ but overall performance is nothing to sniff at and it can run all the same apps.

Performance
7
Features
7
Build quality
9
Usability
7
Value
7
PROS
  • Good value
  • High initial storage capacity
  • Easy memory upgrades
  • Dual M.2 NVMe SSD slots
CONS
  • Less powerful CPU than the DS720+
  • No eSATA expansion port
  • No multi-Gigabit ports
8.8Expert Score
Synology DS720+

The DS720+ and its quad-core Celeron J4125 CPU has a clear edge on performance and will be the best option for more demanding workloads and if you plan on running a lot of apps. It’s ideal if you want to keep your initial spend to a minimum as its expansion port allows capacity to grow with future demand.

Performance
8.5
Features
8.5
Build quality
9
Usability
9
PROS
  • Very good value
  • Quad-core J4125 CPU
  • High performer
  • Easy memory upgrades
  • Dual M.2 NVMe SSD slots
CONS
  • No multi-Gigabit ports
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