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Synology DiskStation DS1621xs+ review: The Lewis Hamilton of desktop storage

A desktop NAS with great features and stunning performance

Editor's Choice
Synology DiskStation DS1621xs+ front and rear
£1,352 exc VAT (diskless)
  • Excellent performance
  • 10GbE port
  • 5-year warranty
  • Dual M.2 NVMe slots
  • PCI-E slot
  • Top data protection apps
  • SSDs can only be used for caching

Synology’s DiskStation DS1621xs+ targets businesses and remote workers that want plenty of NAS power in a compact desktop form factor. This 6-bay appliance is Synology’s first Intel-powered model to sport an embedded 10GBase-T port and it sweetens the deal further with dual M.2 NVMe SSD slots, support for fast DDR4 memory and a spare PCI-E expansion slot.

Costing £1,352 for a diskless model, the DS1621xs+ is a little on the expensive side for a 6-bay NAS, but on the other hand, you’re getting plenty of power for your money. It has a decent 2.2GHz quad-core Intel Xeon D-1527 CPU in the driving seat, partnered by 8GB of DDR4 memory upgradeable to a maximum of 32GB. 

Peace of mind is another bonus, thanks to Synology’s generous 5-year limited hardware warranty. In contrast, most other NAS vendors in this market sector only offer standard 2 or 3 year warranties with paid-for options to upgrade them to 5 years.

Synology DiskStation DS1621xs+ review: Build quality and features

In keeping with Synology’s two-year refresh cycle, the DS1621xs+ is the replacement for the DS1618+ and employs the same sturdy charcoal-black steel chassis. The plastic tool-free drive carriers are spring-loaded and can be locked with the key provided in the accessory box to stop them accidentally popping out. 

A peek round the back shows a few changes, however. Firstly, the quad Gigabit ports of its predecessor have been replaced with dual Gigabit and a 10GBase-T port. You get three USB 3 ports while the pair of eSATA ports can be used to expand outside the box with Synology’s optional 5-bay DX517 desktop expansion units – hence the ‘16’ in the model name.

Synology DiskStation DS1621xs+ software

Memory starts at 8GB and is a cinch to upgrade via two SO-DIMM slots lurking behind a removable hatch underneath the chassis. The M.2 NVMe SSD slots are easily reached by removing the drive carriers to access them in the side panel and for cache testing we fitted two 480GB Kingston DC1000B enterprise-class NVMe SSDs. A detail worth mentioning is that unlike Qnap’s appliances, you can’t use SSDs to create a high-performance storage pool.

The PCI-E slot at the rear is accessed by removing the lid and for our heavy-duty performance tests, we fitted an Emulex dual-port 10GBase-T network card. The appliance uses a pair of 9cm diameter cooling fans protected behind metal grills and small offices will approve of their low noise levels, which we measured at only 39dB from one metre in front.

Synology DiskStation DS1621xs+ review: DSM features

Synology is promoting the DS1621xs+ as its ultimate backup solution, and it’s hard to argue with; its DSM 6.2 software is brimming with data protection apps. The Snapshot Replication app, for instance, handles manual and scheduled snapshots of NAS shares and iSCSI LUNs on Btrfs volumes, which can also be replicated to remote Synology appliances.

Hyper Backup, meanwhile, handles local, remote, Rsync, cloud and iSCSI LUN backups from a single console and the Drive app allows you to create your own private backup cloud with Dropbox-like synchronization services for collaboration and file sharing. The star player, though, is Synology’s Active Backup for Business app which provides a complete on-appliance solution for protecting Windows servers and workstations along with Hyper-V, VMware vCentre and ESXi hypervisors.

Another valuable app (particularly in these challenging times) is the Security Advisor, which scans the appliance at regular intervals for malware and security weaknesses and reports on its finding. The Storage Analyzer app keeps your finger on the pulse for storage usage by running scheduled reports to show NAS share utilisation, duplicate files and file types.

Synology DiskStation DS1621xs+ storage manager

The DS1621xs+ even has the memory capacity to handle virtualization duties and DSM’s Virtual Machine Manager allows the appliance to host VMs running just about any OS you want, as well as supporting extra instances of DSM. It offers protection plans to backup selected VMs using snapshots and it can link up with the ABB app to provide disaster recovery services for bare-metal system and VM backups.

Synology DiskStation DS1621xs+ review: Performance testing 

To test 10GbE performance, we fitted a quartet of 14TB Western Digital Red Plus drives and created a large RAID5 storage pool from the DSM’s Storage Manager. Our test host was a Dell EMC PowerEdge T640 tower server equipped with dual Xeon Gold 5120 CPUs, 64GB of DDR4 plus quad 10GBase-T ports and running Windows Server 2019.

To test maximum performance, we turned to IP SANs where we created a 1TB target and linked the server to it over a triple 10GbE MPIO link. The DS1621xs+ delivered some staggering results with Iometer reporting sequential read and write speeds both of 26.7Gbits/sec and I/O rates with 4KB blocks of 173,000 IOPS and 112,000 IOPS.

For random read and write operations, Iometer recorded 26.7Gbits/sec and 0.74Gbits/sec while I/O throughput was measured at 173,000 IOPS and 3,700 IOPS. Using the Kingston NVMe SSDs as a mirrored read/write cache, we saw random write speed increase nicely to 4Gbits/sec while I/O throughput was boosted hugely to 55,000 IOPS.

The DS1621xs+ is no slouch in the NAS department either: a share mapped to the server over 10GbE returned excellent Iometer sequential read and write speeds of 9.3Gbits/sec and 9.2Gbits/sec. Real-world performance was up there too, and our 25GB file copies averaged 4.5Gbits/sec while our backup test secured a 22.4GB folder and 10,500 files to the share at 2.6Gbits/sec.

Synology DiskStation DS1621xs+ review: Verdict

There’s no doubt about it – the DS1621xs+ is one of the fastest SMB desktop NAS appliances we’ve seen. You’ll be paying a premium for the privilege, since it’s comparatively pricey for a 6-bay NAS, but it clearly has the horsepower to handle the demands of 10GbE connections. 

Expansion potential is particularly good - you have the spare PCI-E slot plus support for up to 32GB of memory, and we’ve shown that M.2 NVMe SSD caches will make substantial improvements to random write operations. Last but not least is Synology’s DSM software which delivers a wealth of features and a sharp focus on data protection, making this the undisputed king of desktop storage appliances.

Synology DiskStation DS1621xs+ specifications




Quad-core 2.2GHz Intel Xeon D-1527


8GB DDR4 (max 32GB)


6 x SATA LFF/SFF, 2 x M.2 NVMe SSD 


Synology DSM

Array support

RAID F1, 0, 1, 10, 5, 6, JBOD


1 x PCI-E Gen3 x8


2 x Gigabit, 1 x 10GBase-T

Other ports

3 x USB 3, 2 x eSATA expansion ports


Internal 250W PSU


Web browser


5 years limited

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