Synology RackStation RC18015xs+

RC18105xs+ controller appliance

Synology has a well-deserved reputation for delivering high-quality NAS appliances and it now takes its first steps into the realms of high-availability storage. Its latest RC18015xs+ is designed to provide failover clustering services for NAS and IP SAN storage and a lot more besides.

The minimum specification is two RC18015xs+ controller appliances which function in an active/passive architecture. Connected via their heartbeat ports, the active controller manages all storage services and if it goes down, the passive controller automatically takes over.

The controllers don’t have integral storage but each has a SAS port which is used to link up to 15 RXD1215sas disk shelves. Expansion potential is quite remarkable as these 12-bay units allow total capacity to scale to nearly 1.5 petabytes although only SAS drives are supported.

RXD1215sas disk shelf

End-to-end redundancy

It’s a truly fault-tolerant design as Synology hasn’t left any single points of failure. Each controller and disk shelf has dual-redundant power supplies and cooling fans while the shelves are connected by dual SAS cables providing fault tolerant links.

Along with their Gigabit heartbeat port, the controllers have four embedded Gigabit data ports and a spare PCI-Express slot for upgrading to 10GbE speeds. All network connections are done in pairs so for every data port used on the master controller, the corresponding port on the passive controller must also be connected to the network.

RC18105xs+ rear view

Deployment is simple enough and we linked the controller’s heartbeat ports using standard Cat6 cable and connected a single RXD1215sas expansion unit using the SAS cables supplied in the box. For testing, we fitted four 4TB WD SAS hard disks and noted that the disk shelf was powered up automatically when we turned on the controllers.

From this point onwards, Synology’s standard discovery web portal takes over. It found the systems on our network and loaded the latest DSM software on them.

The DSM HAM App

The DSM HAM app monitors the cluster while Storage Manager provides an overview of the connected hardware

BTRFS and snapshots

A key feature of the RC18015xs+ is additional support for BTRFS which brings in unlimited snapshots for enhanced data protection. However, Synology hasn’t forsaken the EXT4 file system as you still have this option available when creating volumes.

Synology fans will be very familiar with the DSM web interface which is almost identical to that used by its NAS appliances. For cluster control, Synology has added the High Availability Manager (HAM) app which shows the status of the two controllers and attached disk shelves.

The HAM interface is used to swap the active and passive roles, reboot and power either down or turn off the entire cluster. For disk configuration, we used the standard Storage Manager app to create a RAID-5 array from our drives and then add multiple BTRFS volumes within it.

The new DPM app from Synology

Synology provides the new DPM app for managing BTRFS snapshots and data recovery

The Data Protection Manager (DPM) app now comes into play as shares and iSCSI targets with the protection option enabled can have manual and scheduled snapshots applied. These are really easy to use as you can take them as often as every fifteen minutes and decide how many to retain.

Speedy storage and restores

We opted to move straight to 10GbE for general performance testing and fitted dual-port Emulex fibre SFP+ cards in each controller and connected them to a Netgear 10GbE switch. The controllers have quad-core 3.3GHz E3 Xeon CPUs and 8GB of DDR3 memory so we expected great things from them.

NAS speeds are very good with Iometer reporting raw read and write rates of 1,110MB/sec and 1,098MB/sec for a share mapped to an HP ProLiant DL380 Gen9 rack server. Using our 50GB Iometer test file, we saw sustained read and write speeds for drag and drop copies of 412MB/sec and 400MB/sec.

The RC18015xs+ team handles backup operations well as copying a 22.4GB folder with 10,500 small files returned a very high average of 331MB/sec. It’s no slouch in the IP SAN department either, with a 750GB iSCSI target recording Iometer read and write speeds of 1,058MB/sec and 1,021MB/sec.

We also found data restoration using snapshots very swift as we recovered a 50GB share from its latest snapshot in less than 20 seconds. Another very useful feature is snapshots can be made visible as network shares so users can browse them and restore their own files from Windows Explorer.

Failover issues

HAM warnings

During cluster failover, the HAM warns that all system and applications tasks will be terminated

Using the HAM app to power off the active controller, we watched it post a warning message advising that system tasks, backup jobs and other active apps would be terminated. We continued and after the active controller had been turned off, it took around 90 seconds to promote the passive controller.

During this period we were logged out of the DSM console and could see on our HP server that it has lost contact with all its mapped shares and iSCSI targets. However, once the new active controller was operational, everything was restored to active duty.

Restoring the failed controller is a simple process as when we powered it back up, the HAM app spotted it and configured it as the new passive controller. This phase doesn’t cause any disruption to storage services as our tests continued unabated while the controller was added to the cluster.

PROS:
  • Good storage performance
  • High expansion potential
  • Automated failover
  • Extensive NAS and IP SAN features
  • BTRFS snapshot protection and recovery

CONS:
  • Expensive for an active/passive solution
  • Failover will interrupt services

Summary

With Synology’s DSM at the helm, the RC18015xs+ delivers an unbeatable range of storage features backed up by fault tolerant clustering and BTRFS snapshots. However, our main issues with this solution are it doesn’t provide transparent failover and for an active/passive architecture, it’s expensive.

To put this in perspective, check out our review of Qsan’s new TrioNAS LX U400HA-D424. Along with 24 integral SAS/SATA drive bays, and an equally big expansion potential, its dual active/active controllers provide lightning-quick transparent failover for NAS and IP SAN services and yet it costs slightly less.

7.9 Total Score
Unbeatable Range of Features

With Synology’s DSM at the helm, the RC18015xs+ delivers an unbeatable range of storage features backed up by fault tolerant clustering and BTRFS snapshots. However, our main issues with this solution are it doesn’t provide transparent failover and for an active/passive architecture, it’s expensive. To put this in perspective, check out our review of Qsan’s new TrioNAS LX U400HA-D424. Along with 24 integral SAS/SATA drive bays, and an equally big expansion potential, its dual active/active controllers provide lightning-quick transparent failover for NAS and IP SAN services and yet it costs slightly less.

Performance
8.5
Features
9
Build Quality
9
Usability
7
Value
6
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