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Synology RackStation RS4021xs+

Synology usually operates a two-year refresh cycle on its NAS appliances so the RS4021xs+ is a latecomer to the storage party. Taking over from the three-year old RS4017xs+, this 16-bay rack NAS is aimed at big businesses that want a solid combination of capacity, performance and data protection features.

We’ll get the bad news out of the way first as owners of the RS4017xs+ looking for an upgrade path will be disappointed. Apart from the name change, the only difference between the two models is the RS4021xs+ comes as standard with 16GB of DDR4 ECC memory – twice that of its predecessor.

On the positive side, the RS4017xs+ was Synology’s largest model when it was launched in early 2017 and also one of its most powerful so the hardware spec still has a lot going for it. The RS4021xs+ is powered by an 8-core 2.1GHz D-1541 Xeon CPU and our lab tests show it is an excellent performer.

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Hardware features

We praised the RS4017xs+ for its great build quality so the RS4021xs+ receives the same accolades. The metal chassis is very sturdy, it employs solid metal drive carriers and the price includes two hefty 800W hot-plug PSUs for extra hardware redundancy.

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The RS4021xs+ uses three 8cms diameter hot-plug cooling fans under a separate, removable cover in the lid. For a high-end NAS appliance, general noise levels are quite acceptable although the fans will increase speed noticeably when the appliance is under heavy load.

At the rear are quad Gigabit plus dual embedded 10GBase-T network ports and the two PCI-e expansion slots present plenty of upgrade opportunities. The appliance also offers two high-speed Infinibandports each supporting one 12-bay RX1217/1217RP disk shelf allowing capacity to be increased to 40 drives.

HDD/SSD compatibility

At the same time it announced the RS4021xs+, Synology launched its own HAT5300 SATA HDDs which are currently available in 8TB, 12TB and 16TB capacities. More significantly, it introduced a new policy for its enterprise-class NAS appliances that only allows validated drives to be used in them.

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Naturally, this includes all HAT5300 HDDs and SAT5200 SSDs with the RS4021xs+ compatibility list also including four low-capacity models from Seagate, Toshiba and Western Digital. The bottom line is you must only populate the appliance with storage devices on the compatibility list.

The HAT5300 drives are manufactured by Toshiba and use Synology’s modified firmware which it claims offers a higher performance and enhanced reliability. A glance at the HAT5300 spec sheet shows they have 2.5M hour MTTF and 550TB yearly workloadratingsplus a 5-year warranty putting them on a par with Toshiba’s own MG Series and Seagate’s Exosenterprise drives.

Compatibility testing is a laborious and expensive process and we can see the reasoning here as this move allows Synology to provide a complete support package for its enterprise products. Let’s face it, all blue chip server and storage array vendors do it, so why shouldn’t Synology?

Another bonus when using certified drives is Synology’s DSM software will keep their firmware automatically updated for you. We tested the RS4021xs+ using four 8TB HAT5300 drives and noted that the Storage Manager app provides a manual firmware update service as well.

We also checked what happens if you use uncertified drives and fitted four 14TB WD Red Pro drives. The DSM Storage Manager allowed us to create RAID arrays, storage pools and volumes but warned that the appliance was in danger as all drives were unverified and wouldn’t provide any SMART status information either.

10GbE performance

For 10GbE performance testing, we created a 22TB RAID 5 storage pool from the four HAT5300 drives and used a Dell PowerEdge T640 tower running Windows Server 2019 as our host. The RS4021xs+ delivers in the speed stakes as a NAS share mapped over 10GbE returned excellent Iometer sequential read and write rates both of 9.3Gbits/sec.

Real world speeds are just as good with drag and drop copies of a 25GB test file delivering average read and write speeds of 5.3Gbits/sec and 5.1Gbits/sec. Our backup test secured a 22.4GB test folder and 10,500 small files to a share at 2.6Gbits/sec while copying the 25GB test file to an encrypted folder averaged a speedy 2.7Gbits/sec.

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For IP SAN testing, we started with a single 10GbE link to a 1TB target and watched the RS4021xs+ match NAS performance with Iometer sequential read and write speeds of 9.3Gbits/sec. Adding another Synology dual-port 10GbE adapter to the appliance, we created a quad 10GbE MPIO to the target and watched Iometer read and write rates jump up to 36.6Gbits/sec and 17.7Gbits/sec.

Main DSM features

Synology is promoting the RS4021xs+ as the ultimate backup solution and its DSM software seals the deal with a wealth of data protection services and apps. You have scheduled snapshots on BTRFS volumes while the Hyper Backup app manages all local, remote, Rsync, cloud and iSCSI LUN backups from a single console.

The free Active Backup Suite provides centralized backup services with the Active Backup for Business (ABB) component securing servers and workstations plus VMware and Hyper-V virtualization hosts and all their VMs. Two separate suite members are provided for protecting Microsoft 365 and Google Workspace.

The Surveillance Station app can transform the appliance into a sophisticated recording vault with its wealth of video management services and supportfor over 7,600 IP camera models. Virtualization is on its agenda too, with the Virtual Machine Manager capable of hosting just about any OS you care to name, including virtualized versions of DSM.

Conclusion

The RS4021xs+ teams up a high storage capacity with good expansion potential and excellent 10GbE performance. There’s nothing here to tempt existing RS4017xs+ owners to upgrade, but it’s a great choice for businesses looking for a versatile storage appliance at a good price – just make sure you pay close attention to Synology’s hardware compatibility lists.

SYNOLOGY RS4021xs+ 144TB (12 x 12TB) integrated w/ High-Performance HAT5300-12T Synology drives.
Synology RS4021xs+ diskless 16 bay Rackstation 2U NAS, Intel® Xeon® D-1541 8-core 2.1 GHz CPU, 8 GB DDR4 ECC UDIMM, upgradable to 64 GB (16 GB x 4).
$ 10,399.00
Synology RackStation RS4021xs+
8.5Expert Score
Good value

The RS4021xs+ teams up a high storage capacity with good expansion potential and excellent 10GbE performance. There’s nothing here to tempt existing RS4017xs+ owners to upgrade, but it’s a great choice for businesses looking for a versatile storage appliance at a good price – just make sure you pay close attention to Synology’s hardware compatibility lists.

Performance
9.5
Features
8
Build quality
8.5
Usability
8.5
Value
8
PROS
  • Good value
  • Top 10GbE performance
  • High storage capacity
  • High expansion potential
  • Dual 10GbE ports
  • Feature rich DSM software
CONS
  • Pay attention to the hard disk compatibility list
  • Exactly the same hardware as the older RS4017xs+

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