Synology DiskStation DS2015xs Review

Synology’s latest DS2015xs stands out from the NAS crowd for a number of good reasons. For starters, it’s the very first desktop appliance to come with a pair of integral 10GbE SFP+ fiber ports.

It also introduces Annapurna Labs and its new Alpine AL-514 processor. Formed in 2011, this Israeli start-up is being particularly coy at the moment as its web site tells you nothing and when asked, Synology couldn’t furnish us with any more details about it either.

What we can tell you is the Alpine AL-514 is a quad-core ARM-based SoC (system on chip) running at 1.7GHz. It allows the DS2015xs to support up to 8GB of DDR3 memory but what makes it unusual is it’s one of the first ARM SoCs to deliver dual, embedded 10GbE SFP+ ports.

Annapurna Labs is already proving popular this year as Netgear and QNAP has announced a range of SOHO NAS appliances featuring its ARM-based SoCs. Both the 1.2GHz and 1.4GHz dual-core versions appear across these product ranges but none feature the integrated 10GbE ports.

Cabling conundrums

The DS2015xs looks very affordable but it doesn’t come with any transceivers so you need to factor in these costs as well. The ports are industry-standard SFP+ (enhanced small form-factor pluggable) and the DS2015xs supports 10GBase-SR and 10GBase-LR transceivers from Avago and Finisar.

In the lab we use Avago AFBR-703SDZ 850nm 10GBase-SR transceivers which are on Synology’s list of supported transceivers and cost around $200 apiece. We can’t see anyone wanting to fit expensive 10GBase-LR 1310nm transceivers which support 10km cable distances.

If you’re planning on sharing the 10GbE wealth across your network, you also need to consider the cost of an appropriate Gigabit network switch with dual 10GbE SFP+ uplink ports and a pair of transceivers for it. Another alternative is copper direct attach cables with built-in transceivers but Synology’s list of supported cables is currently limited to five from vendors such as Axiom, Cisco and HP.

10GbE NAS performance tests

The DS2015xs provides dual embedded 10GbE SFP+ ports along with a couple of Gigabit as well.

The DS2015xs provides dual embedded 10GbE SFP+ ports along with a couple of Gigabit as well.

For speed testing we used a Dell PowerEdge R730 rack server equipped with dual 14-core E5-2695 v3 Xeons, 64GB of DDR4 memory and Windows Server 2012 R2. We fitted an Emulex OCE11102-NM dual port 10GbE adapter and used our Avago 10GBase-SR transceivers.

On the DS2015xs, we fitted the same Avago transceivers. For storage, we loaded up six 4TB WD Red SATA hard disks and created a single RAID5 array from them all.

NAS performance is good as with a share mapped to the Dell server over a single 10GbE connection, we saw Iometer report raw read and write rates of 1050MB/sec and 1005MB/sec. Real world speeds are very fast with drag and copies of our 50GB Iometer test file returning sustained read and write speeds of 609MB/se and 581MB/sec.

Backup speeds over 10GbE are good as well with our 22.4GB test folder containing 10,500 small files copied across to the DS2015xs at an average of 269MB/sec. QNAP’s TS-EC880 managed a noticeably slower 203MB/sec for this test.

IP SANs – could do better

The DS2015xs gets the benefit of Synology’s DSM 5.1 software so it’s packed with storage features

IP SAN testing initially proved to be problematic as we couldn’t get any decent speeds out of the DS2015xs. In the end, the best results we achieved were with 9000 MTU Jumbo frames enabled on the appliance and test server.

With Iometer using a 50GB test file and set to a 256KB request size and 16 outstanding I/Os, we saw it report a 972MB/sec raw read rate for a 600GB iSCSI target. Write speeds were unimpressive with the DS2015xs returning 497MB/sec while dropping to a 4K transfer request size saw only 15,600 IOPS for sequential reads.

Setting up a dual 10GbE MPIO link was simple enough but performance improvements were unimpressive with raw read and write speeds only increasing to 1160MB/sec and 550MB/sec while IOPS remained the same. We also noted CPU utilization during these MPIO tests peaked as high as 84%.

We did have long discussions with Synology’s support about our performance tests. The bottom line is its published results were achieved using a high-performance 8-drive RAID5 arrays comprising 240GB Intel 520 Series SSDs.

SSD caching

The DS2015xs supports both read and write caching using SSDs although you’ll need two identical SSDs to use this. If you opt for a read cache, the appliance creates a stripe from them and for a read/write cache, it’ll create a mirror.

Synology’s SSD read/write caching delivers a big boost to IOPS

To test caching we configured an Iometer SQL database simulation using 256 outstanding I/Os, a 16KB block size, 66% read, 34% write and a 100% random distribution. On an un-cached iSCSI target this returned a steady 182 IOPS.

We added a pair of 120GB OCZ SSDs, created a read cache from them and reran the Iometer database load, After around four hours, the cache was full of hot data and Iometer gradually ramped up to 295 IOPS.

Next, we created a read/write cache using the two SSDs and ensured the Iometer test file was fully cached. Rerunning the test now returned a much higher 3,000 IOPS showing clearly the benefits of Synology’s write caching.

PROS:
  • Integral 10GbE SFP+ ports
  • Top 10GbE NAS performance
  • SSD caching boosts IOPS
  • High expansion with Infiniband port
  • Cheaper than current 10GBase-T equipped appliances

CONS:
  • Factor 10GbE transceivers into costs
  • Poor IP SAN speeds

Summary

The DS2015xs is certainly an unusual storage appliance but is let down by unimpressive IP SAN speeds over MPIO links. However, it’s packed with plenty of storage features, NAS performance is a lot better and it scores highly for value as it delivers integral 10GbE networking at a comparatively low price.

Netgear’s 6-bay ReadyNAS 716, for example, comes with dual 10GBase-T ports as standard but costs upwards of $3,000 for a diskless unit. Prices for a diskless DS2015xs start at $1,399 but even after including the cost of the SFP+ transceivers, it still comes out on top by a long way for value.

8.4 Total Score
Plenty of Storage Features

The DS2015xs is certainly an unusual storage appliance but is let down by unimpressive IP SAN speeds over MPIO links. However, it’s packed with plenty of storage features, NAS performance is a lot better and it scores highly for value as it delivers integral 10GbE networking at a comparatively low price. Netgear’s 6-bay ReadyNAS 716, for example, comes with dual 10GBase-T ports as standard but costs upwards of $3,000 for a diskless unit. Prices for a diskless DS2015xs start at $1,399 but even after including the cost of the SFP+ transceivers, it still comes out on top by a long way for value.

Performance
7
Features
9
Build Quality
9
Usability
8
Value
9
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