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Synology DiskStation DS1621xs+ Review


Stepping up as the replacement for the DS1618+, the DS1621xs+ targets SMBs that want more power to their desktop storage as it delivers the same six hot-swap drive bays but teams them up with an embedded 10GbE port. There’s more as it supports dual M.2 NVMe SSDs for use as a performance enhancing cache and has a PCI-E expansion slot so you can add even more 10GbE ports.

This isn’t Synology’s first desktop appliance to feature embedded 10GbE ports as this honor goes to the 8-bay Value series DS1817 which is now in its third year. It’s an oddball appliance as it comes with dual 10GBase-T ports but their potential will never be realized as performance and app support are hobbled by its feeble Annapurna Alpine AL-314 32-bit CPU and sluggish DDR3L memory

No such restrictions with the DS1612xs+ as it’s powered by a 2.2GHz quad-core Intel Xeon D-1527 CPU partnered by 8GB of faster DDR4 memory which can be upgraded to 32GB. Expansion potential is good as the ‘16’ in this appliance’s model name indicates that its dual eSATA ports support Synology’s optional 5-bay DX517 desktop expansion units.

DS1621xs+ Great build quality

DS1621xs+ performance is amazing

10GbE sequential and random read performance for IP SANs is simply amazing

Whereas Synology’s latest Plus series of appliances use cheaper plastic casings, the DS1612xs+ is endowed with a more reassuring solid metal chassis and cover. The hot-swap drive carriers are the tool-free variety and are spring-loaded so they pop out with a finger tap (they can be locked as well).

The PCI-E slot sits to one side at the back and we had no problems fitting an Emulex dual-port 10GBase-T network card. Memory upgrades are a cinch as the two SO-DIMM slots are located behind a metal hatch underneath so you don’t need to remove the lid.

Adding NVMe SSDs is simple too, as the M.2 slots are accessed by removing the drive carriers where you’ll find them lurking to the left-hand side. The high-speed 10GbE port makes caching more appealing and for testing, we slipped in a pair of 480GB Kingston DC1000B enterprise-class NVMe SSDs.

The DS1612xs+ also has a built power supply as opposed to the power bricks used by the Plus series of appliances. Cooling is handled by a pair of 9cms diameter fans behind metal grills as we found noise levels to be very low.

DS1621xs+ 10GbE and caching performance

DS1621xs+ VM Manager

The DS1621xs+ has the power and memory to run the Virtual Machine Manager app for hosting other operating systems

For testing, we installed four 14TB Western Digital Red Plus NAS-specific drives and used DSM’s Storage Manager to create a large RAID5 storage pool – Synology’s entry-level SHR arrays aren’t supported by this appliance. With a share mapped over a direct 10GbE connection to Dell PowerEdge T640 Xeon Scalable tower server running Windows Server 2019, we recorded top Iometer sequential read and write speeds of 9.3Gbits/sec and 9.2Gbits/sec.

Real world performance is good with copies of a 25GB test file averaging 4.5Gbits/sec in both directions. Copying the same file to an encrypted folder averaged 2.2Gbits/sec while backing up a 22.4GB folder containing 10,500 small files returned a speedy 2.6Gbits/sec.

For IP SAN testing, we created a triple 10GbE MPIO link to a 1TB target and watched the DS1621xs+ deliver some stunning results. Iometer recorded sequential read and write rates both of 26.7Gbits/sec and I/O rates with 4KB blocks of 173,000 IOPS and 112,000 IOPS.

Swapping to random operations saw read and write rates of 26.7Gbits/sec and 0.74Gbits/sec while throughput numbers were 173,000 IOPS and 3,700 IOPS. To test caching performance, we created a mirrored read/write cache from the Kingston NVMe SSDs and applied it to our hard disk volume.

As expected, we saw no significant benefits for sequential reads and writes or random reads. Random writes received a big boost though, with Iometer reporting a 436% increase to 4Gbits/sec and an I/O throughput increase of 1,386% to 55,000 IOPS.

DSM business features

Synology DSM

DSM offers a superb set of data protection tools including the Active Backup Suite and Snapshot Replication apps

Synology is promoting the DS1621xs+ as a high performing all-rounder that’ll satisfy all your business storage requirements. We can’t argue with this as along with great performance, Synology’s DSM software delivers plenty of apps covering everything from backup, data protection and private clouds to file serving, collaboration and virtualization.

For the latter, the Virtual Machine Manager app can host just about any OS you care to name, including virtualized versions of DSM. It’s easy to use and we created a Windows Server 2019 VM from an ISO file in only 20 minutes and could back it up by taking regular scheduled VM snapshots.

On-appliance data is protected by BTRFS snapshots on NAS shares and iSCSI LUNs which can be scheduled or run manually from the Snapshot Replication app. Hyper Backup manages all your local, remote, Rsync, cloud and iSCSI LUN backups from a single console and integrates with Synology’s optional C2 Backup cloud service for off-site storage.

The slick Active Backup Suite turns the appliance into a fully centralized backup vault as the free Active Backup for Business (ABB) component can secure servers and workstations plus VMware and Hyper-V virtualization hosts and all their VMs. The suite also provides separate apps for protecting G Suite and Office 365.

You can keep a close eye on capacity as the Storage Analyzer app runs regular reports to show usage for NAS shares, duplicate files and file types. The Security Advisor helps keep your appliance safe by scanning it regularly for malware and security issues such as open ports or weak passwords and offering sage advice on closing any potential holes.

Synology DS1621xs+
High-end scalable NAS in desktop form factor
Synology DiskStation DS1621xs+ Review


Everything about the DS1621xs+ exudes quality and it’s faster than the Atom-powered DS1618+ – a lot faster. Costing nearly $1,600, it may be comparatively expensive, but you’re getting plenty of hardware for your money including a 10GBase-T port, PCI-E slot, dual NVMe SSD cache slots and a high external expansion potential.

Synology’s DSM software is packed with features and apps making it a great choice for a wide range of businesses. Performance over 10GbE is impeccable and the icing on the cake is the price includes a 5-year hardware warranty.

9 Total Score
Worth the Price

Everything about the DS1621xs+ exudes quality and it’s faster than the Atom-powered DS1618+ - a lot faster. Costing nearly $1,600, it may be comparatively expensive, but you’re getting plenty of hardware for your money including a 10GBase-T port, PCI-E slot, dual NVMe SSD cache slots and a high external expansion potential.

Build quality
  • Superb performance
  • Embedded 10GbE port
  • Expansion slot
  • NVMe SSD suppor
  • Feature-rich DSM software
  • 5-year warranty
  • A little pricey for a 6-bay NAS

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