REVIEW: Synology DiskStation DS1515+, Love at First Byte! [TOP 15 of 2015]

REVIEW: Synology DiskStation DS1515+, Love at First Byte! [TOP 15 of 2015]

Editor's Note:
The following article, 
originally published on January 6, was AkihabaraNews' #1 most popular of 2015. It is also - without doubt - the dorkiest. We love that. [Check out the full Top 15 of 2015 list here.]

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It’s been over a year since we last had the time to put a new NAS unit to the test. Today, the upgrade to Synology's 5-bay dream was left at our doorstep, so what else could we do than take this new DS1515+ powerhouse for a spin?!

This peculiar black box looks a lot like its predecessors. Most of the upgrade improvements relate to power efficiency, general performance, and maximizing usability. The DS1515+ puts itself between a big brother (8-bay) DS1815+ that shares the exact same quad-core power specifications as the DS1515+, on the opposite end there’s the 4-bay DS415+, and the previous model of the 5-bay NAS (DS1513+) is also still on the product list. Has to be added, however, that it’s likely the DS1513+ will be suspended in the next few months since that unit still sports the previous generation dual-core processing unit (with all due respect, the DS1513+ was no slouch).

Ike’s December 2013 Review of the Synology DS1513+
All Synology Reviews at the Old Site (they are legion!)

Synology DS1515+ Key Features

  • Ultra-performance NAS optimized for intensive tasks and encryption
  • 2.4Ghz Quad-core processor, hardware encryption engine, and flawless software integration
  • Powerful, expandable 5-bay NAS server
  • Delivers outstanding speed and accelerated data encryption
  • Easily scalable, the DS1515+ can be equipped with up to 6 GB of DDR3 RAM and host up to 90TB of raw capacity with two Synology DX513 units.

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Looks & Impressions

The DS1515+ has a lot in common with...actually, we can almost copy what we wrote about the DS1513+ as it’s about 99% identical.

Synology already had an established and very respected unit with the very first generation of their 5-bay NAS. Strong sales worldwide, based on a proven design, made the company decide they shouldn’t change a winning team. Thus, the new DS1515+ looks pretty much identical to its predecessors (leaving aside the few cosmetic changes, the type number for one...).

The matte black-colored outer shell still consists of thin rolled steel; the front bezel is made of PVC. Everything looks well built and lives up to the business appeal. The 5 drive bays are the exact same push-tray system used for most devices in the SMB series, all very durable with a no-nonsense approach to design. A nice feature is the twist-locking mechanism, which prevents trays to snapping out if accidentally pushed. In previous models, the push-trays required using the little bolts to make sure the hard drives stuck in place. With this new tray version, Synology incorporated a snap (tool free) system where, technically speaking, you don’t need to posses a screwdriver anymore. :)

On the back of the unit, the blue color on the USB ports reveal the upgrade to USB 3.0 ports. The fans are 2x80mm models; equally kept intact are the dual ESATA connectors for the expansion unit(s).

The power unit for the DS1515+ is integrated, but it is very easy to replace should ever fail to function properly. The power unit was made by Delta Electronics (a very reputable name in the world of reliable business supplies) and is rated up to 240W, so you have an excess of juice left even after you filled up your NAS with hard drives.

It may not be the most weighty argument for your purchase decision, but the soft silicone feet of the DS1515+ are one of the best vibration suppressors I've seen on a NAS unit. After the weight of the NAS increases (filled with hard drives), they provide excellent grip as well.


Full spec sheet available here.

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Setting up the new DSM

The new DSM 5.1 really is a charm to work with, and we will start with running you through the basics on how to set up the DS1515+ (which in essence is pretty much the exact same procedure for other models, only the RAID options will change depending on the amount of bays available).

1. The best way to get this unit detected (for non tech gurus) is to download & install Synology Assistant. It’s free of charge and available on their website for various platforms. Once the software is installed, the new unit will show up as “DiskStation” in the list. Double click it, and the web interface will open.

If you currently have multiple DiskStations in your list, the new one will mention “Ready for Migration” (or install if the drives have not been used in a previous Synology NAS before).

2. Once you are logged in to the DSM web interface, you'll get a lovely warning that you may lose all data etc., etc., etc...no worries, just click accept. In the next step you will be able to choose if you want to migrate (keep all settings & data intact) or start with a clean sheet (data generally is kept intact).

3. Migration is only useful if you swap your hard disks from an old Synology NAS to this DS1515+ and wish it to run “as it was the old one.” The clean sheet option is what we choose for testing, however, I admit that the warnings of deletion are a bit overrated. As the system installed the DSM and still knew these test hard disks were used in a RAID1 test, so I ended up with a “clean” DSM to configure, but the unit kept all the data from a previous test intact. This may be good to know for those of you who accidentally chose a clean install and were thinking the *** hit the fan.

4. Once installed, it will prompt you to pick a password (this is for the admin user, later you can create all the additional accounts, folders, user folders and hidden folders your heart desires).

5. In the next step, it will ask you if you wish to install 6 recommended packages (video station, photo station, surveillance, etc.). You can click skip this step if you wish to only install what you are going to actively use later. After this step you will get a short “guided tour” of the new DSM, and it’s strongly recommended that new users to run through this.

6. By now you have access to configure your unit, create new folders and users, and manage all advanced security and disk configuration options available. As this is something entirely up to personal flavor, we will let you play around yourself.

7. If all went well, the diskstation should give a Green checkmark saying “Your diskstation is working fine.” Obviously, when we started configuring ours, karma invited itself over and one of our hard disks failed to pass the integrity tests (which is very “notifying,” as your unit will keep beeping non-stop). The advantage of this unit is, it will display a warning you can click to open the menu item where you can disable all beeps. Replacing the hard drive and upgrading from Raid 1 to Raid 5 is easy as ABC once you start to get familiar with the step-by-step guided procedures.

NOTE: I personally recommend disabling ALL and ANY beep notifications, just use the email or sms function to notify you when a volume crashes. Reason being, let's assume you're on holiday/business trip (or your IT Guy is). If a volume crashes, or simply 1 of the fans malfunctions (which isn't going to kill the unit) the device will keep beeping non-stop. This is not Mozart playing, and I assure you after 1 minute this gets on your nerves, after 20 minutes it will bring you to the brink of madness, and without admin access it won't stop itself. Well, not without unplugging the power cord. :)

SSD Caching - Oh Yes, Oh Yes!

One of the cool features of the new DSM is the SSD Caching feature. If you intend to put 1 SSD in your NAS, the DSM can determine which data is considered “hot” (frequently used) and thus cached on the SSD. This may not greatly benefit a home user who is using their DiskStation for general media purposes. For enterprise users and demanding server environments its a different story.

By caching the SQL databases (when used as a web station) or commonly accessed documents in multi-user scenarios, this technology integrated in the DSM 5.1 creates a snappy, instant interaction with your NAS. Whereas, in case of multiple users, the constant search actions on physical spinning disks would have seriously reduced the response times.

That said, for most SMB this may only result in millisecond benefits, only when 50 or more users start to log on and actively use the unit, then this SSD caching will be a most welcome asset to have.

When using the DS1515+ for web server purposes, I would advise you to use 2 mirrored hard drives for the website content, an SSD for the databases, and another 1-2 SSDs for caching. You can also add a USB 3.0 external SSD drive for caching. The more caching SSDs you add, the higher the response times. Please refer to Synology's white paper (see below) to learn how to boost your DiskStation's read/write response timing anywhere from 232% up to 421% improvement.

Synology recommends not using an SSD larger than 128 GB for the default 2 GB of RAM that ships with the unit. Once you increase the RAM, the SSD capacity can be increased up to 1Tb. It is interesting to read the white paper tests from Synology.

NOTE: SSD Caching is not available on DiskStations in the home/entertainment segment, only SMB and Enterprise units with 4+ bays will support this innovation.

Getting the Most of It

As business IT professionals usually are well aware what they can achieve with the luxurious availability of 4 LAN ports on the back, I wish to point out a few useful tricks of the trade for not so technically accomplished readers who wish to get the most of their DIY setup of the DS1515+

As a general scenario (as often is the case): a NAS having 2 or multiple LAN ports, yet all traffic gets routed to 1 plugged-in RJ45 (gigabit port 10/100/1000) = a bad idea! Why? Well, given that you’re using 1000 Mbit network interface (the one most computers and notebooks have), 1000 Mbit divided by 8 bits gives you roughly 112 Megabytes per second this port can handle.

So? Well, if you let your internet, mails, file sharing, print server, external usb backup, surveillance or web server all run over that 1 single port. You are making all these services bottleneck down to the maximum transfer speed.

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Solution: if you have 4 Network ports, just like the DS1515+, why not actually open up the 4x +-112Mb resulting in nearly 450 Mb per second? In my case study, I have a macbook with 2 thunderbolt ports (thus 2 convertors to RJ45 10/100/1000 Ethernet). The macbook is the most important device in the SOHO setup, so the most dedicated speed should be reserved at all time for it. How I do this? I'll tell you:

LAN 1: you can use a Synology NAS directly connected to any other device without the need of “a network” or Ad-Hoc (after the device is configured). What this means is, on LAN 1 I plug in an ethernet (patch) cable, and the other end I plug in thunderbolt port 1 (via convertor). By assigning the IP range on the Synology DiskManager (in Network, and under LAN 1, choose Manual with DHCP), you can enter a random network range that does not interfere with your local network's range. For example I used: (the average home/office will have a range starting with 198.168.x.x, so that pattern you’ll want to avoid).

The second step to make this work on the PC/Mac's side is going to the Network Settings and assigning the port where it’s plugged-in to a corresponding manually set IP address in the exact same range as the number used on the NAS. In my example, the NAS is, so I made the PC/Mac port You only need change the last three numbers in that sentence, anything from 102 to 999 will work just fine.

Now, what we just created is your own private direct connection to the DiskStation DS1515+ without the need of any routers or network switches. Since its a direct connection, it is also considered a private line with +-112.5 Mb/s, which I predominantly use when editing photo or video over the network because I know nothing else in the network can affect the speed on this “lane.”

Cool huh? Well it doesn't stop there, if you are having a receiver with network support, you can equally configure it to work on a separate line from the DS1515+ to your receiver. That also guarantees that these heavy bandwidth media devices won't guzzle up the largest amount of speed.

LAN2 + LAN3: Usually with 1 port NAS devices, that 1 port is going to be plugged into your generic network's switch that's going to provide all your devices at work/home/office environment their network connectivity needs. All fine & dandy, but what If that +-112.5 Mb/s on that port is becoming zipped by a few users who were in the middle of transferring a few heavy files to each other?

That's where link aggregation comes to the rescue! In essence we are using 2 (or more) ports to provide a technical +-225 Mb/s of available speed to the users connected on your switch. Please check this document from Synology to see how to do this very easily.

NOTE: yes, your notebook/PC will still be limited to its own +- 112,5Mb/s (unless it has 2 network ports supporting Link Aggregation too), so be aware, even if you start to link up all 4 RJ45 ports on the DS1515+, it will not give you alone a 450Mb/s transfer speeds. Because the device you wish to receive it, will always be the limiting factor in the equation.

LAN 4: So we already used up 3 out of 4, what else can we do...well there is a plethora of choice left where separate RJ45 dedicated speed can be useful: a web server (be it only for intranet, or extranet) or surveillance station, as examples. Or, you could decide to give iSCSI LUN's a try with all the virtualization bliss you can wish for (remote booting, useful for POS or terminals). As a last alternative, you can use your Synology NAS as a personal cloud by only opening this particular port to accept incoming connections from WAN derived traffic (internet).

Small Modifications

MOD #1: By default the unit ships with 2 GB SODIMM, its incredibly easy to replace or add (1 free slot) RAM. I tested by adding another 4 GB regular “over-the-counter” 1600Mhz laptop memory. The memory was accepted immediately, so I do not expect many people will have problems upgrading to the brand of SODIMM they prefer.

MOD #2: I guarantee that I have turned the DS1515+ on every side, examining on how I could make it even better. Synology has a very strong near-perfect interior with their 5-bays, its all very rigidly built and the welded frame makes a sturdy finished piece. So...if the iron doesn’t rattle, we'll look close at that PVC. Bingo: the brackets used for the hard drives have little friction between the bracket and the disk rails, and there is a little bit of noise generated from the 0.5mm gap (which does make tool-free replacing drives a charm). What I did here was used a rubber strip about 0.5mm thick/1cm width (every DIY store has some sort of pond liner or similar strips usable for this purpose) and glued one on top and bottom of the brackets. This assured the brackets are pretty much locked in the holders. And the rubber on both sides absorbs that extra bit of vibration.

NOTE: rubber strips don't slide as easy on the PVC rails, lightly wet the top and bottom with a sponge (regular tap water) and then slide them in. Once dried, the drive brackets will be perfectly stuck in the enclosure's rails.

MOD #3: Replacing the 2x 80mm fans. Whiile claimed to be only 22DB, still they were too audible when in close proximity to your working environment. So, Noctua sent us over 2 super-silent 80mm fans, backed with a 6y warranty. Noctua sells 3 models of 80mm fans, varying from 10 up to 18DB max (they always can be reduced in speed so technically its easy to keep any of them at a dead-mouse silent level).

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As seen in the table above, we are getting about the exact same airflow, yet we're reducing the noise by almost half the decibels. Good to see how cleverly optimized blades can produce the same airflow at 900 RPM less, isn't it?

There is also the ULN version of our model listed, it does a bit less airflow, but don't be discouraged by the lower number, as the DS1515+ sets the fan speeds depending on the hard disks temperature, this means that even the default fan rarely spins at its full capacity. If you wish to use the ULN model (at a mere 10.4 DB) and you set the fan speed in the DSM to maximum, the chance your disks will ever get hot is almost zero to none.

Smart tip for the noise purists out there: the less airflow gets obstructed, the more silent your unit will be. So, what I tend to do with NAS units, is fill up any “open air zone” with sound suppressing foam. Open air zones are usually the top and bottom of the disks, do not put foam between the disks, that's the zone we want to keep the most air flowing through. Another helpful trick, is to cut out the radiator grills. May sound stupid, but these bits of plastic obstruct airflow too.

NOTE: Yes its “very dangerous” when the grills are out to harm your fingers when touching the rotating fans. If you want to do it, don't be a wussy about it, its not a garden shredder.

Test Results

Provided below is a simple table of file read/write actions we performed which represent a real world approximation of what users actually do with their NAS devices. These tests are averages from Windows (SMB) and Apple (AFP) systems.

Test Content:

  • A set of 100 HQ JPEG photos in folder
  • 1000 itunes audio files
  • A 4 GB folder containing mixed small files and folders (comparable with a backup)
  • An 8 GB single file archive
  • A 35 GB folder with 10 3.5 GB files inside
  • An 800MB single file archive
  • A 350MB episode Test: RAID5 ( 3 disk mode)

This unit has only been tested in Raid5 as this is the most common setup for SMB usage, which ensures that your data maintains high availability combined with superior data protection in this RAID derivative.

The default supplied Synology network cables (by default 2x shipped in the box) were used. The peak speeds were only attained when testing on a direct line from the NAS's RJ45 to an Ethernet to Thunderbolt convertor.

NOTE: Test results were derived from network analyzing tools like ObDev's Little Snitch network capture, yet this 147Mb/s is what Apple's built in network activity monitor claims to be the top speed. In general the averages read by the activity monitor in OSX Yosemite are different than OSX Mavericks or older. This just to show you, that correct LAN monitoring isn't always happening through the OS itself, as Synology's built-in network monitor never pushed values this high (when logging in to the DSM and match both DSM network monitor VS OSX built-in monitor VS ObDev's Little Snitch.


Simply put, the DS1515+ is hands-down our new favorite amongst all Synology products we've tested in the past.

Editor’s Note: 
That’s no small statement; Ike has been reviewing Synology products for over 4 years! Look here for the archive, and more recently, check out his take on this unit’s predecessor, the DS1513+.

This new Intel Atom C2538 2.4Ghz quad-core CPU really elevated the game: the new unit features built-in floating point and encryption AES-NI combined with almost 10% reduced power consumption while producing bursts over twice the computational power of its predecessor.

When testing the Synology DS1515+, we noticed something quite peculiar: if the unit was connected to our switch (Gigabit TP Link), the top performance (per port) always hit the wall at around 119 Mb/s. However, when testing on an RJ45 to Thunderbolt convertor, we experienced up to 27 Mb/s speed gain over the direct line (top performance reaching 147Mb/s). It's hard to believe these kind of results. We always compare a LAN monitor (Little Snitch from ObDev) vs. Synology's built-in network activity monitor vs. OSX's built-in network activity monitor, and since Yosemite, we have to say the throughput claims aren’t up to par with the dedicated network monitoring solutions (DSM or Little Snitch, respectively) whose results are generally considered highly credible.

NOTE: For readers on OSX who wish to test the speeds of their NAS units, I would recommend giving Little Snitch from OBDev a try. You can find a free demo version here. Personally I find it one of the most effective and straightforward firewalls made for the OSX platform.

To round up, the Synology DS1515+ is stable, very, very stable and consistent. Compared to the previous DS1513+, it boosts the speed both in read and write. The data transfer speed intervals are more gradual, with less differentiation in min/max spikes. Literally, this black box will push your network cables/switches to their limit.

Video editors, photographers, and media professionals working with large files will consider themselves blessed by purchasing a new DS1515+. When you add an SSD to it, upgrade its DDR RAM, and start using it for database/VM or web server purposes, the quad core powerhouse transforms from “mere NAS” to your personal cloud + potent dedicated server. Priced at 750 USD/EUR give/take depending on exchange rates, it just doesn't get much better in price/performance.

Lastly, apologies for the longest NAS review we've written so far. It’s no lie if I say that, for networking professionals, the Synology DS1515+ will be love at first byte.

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