Synology DS1520+ DiskStation Review

Last Updated: May 13, 2023

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As part of revamping my data backup and archiving strategy, I was looking for a network storage solution that could replace my directly-attached storage devices consisting of a LaCie 5big Thunderbolt 2 RAID and a 5TB LaCie D2 drive. The latter I used to maintain an extra copy of the most critical data I had stored on the LaCie RAID.

My goal was to find a solution that I could install on my wall or server rack, rather than having to connect it directly to my iMac Pro via USB-C or Thunderbolt. 

Synology is one of the leading manufacturers of network-attached storage (NAS) solutions and has been on my radar for a long time. When I finally decided to pull the trigger and replace my LaCie setup, I reached out to Synology and they were kind enough to send me their brand-new Synology DS1520+ 5-Bay DiskStation.

While the five-bay DS1520+ can undoubtedly hold its own, I also decided to purchase the Synology RS1219+ — an eight-bay rack-mounted NAS that would become my data storage hub. I envisioned the DS1520+ serving as a mirror of the RS1219+ and acting as my primary TimeMachine backup drive. 

Time Machine is the native backup solution of macOS.

In this review, I’ll tell you everything you need to know about the DS1520+, the critical performance differences between NAS and DAS (direct-attached storage), and why I wish I had bought a Synology storage solution much sooner. 

Synology DS1520+ 5-Bay NAS

Michael Kummer

Synology DS1520+ - Angle


The Synology DS1520+ is an excellent choice for all users who are looking for a data storage solution that’s easy to install, that provides superior data protection in case of hardware failure, and that can grow with your data.



  • Sufficient performance for most use cases
  • Powerful operating system
  • Plenty of expansion ports
  • Expandable to 15 drives


  • No 10Gbit Ethernet
  • Memory can’t be upgraded

Synology DS1520+ 5-Bay NAS Review

Synology DS1520+ - In wall rack
The Synology DS1520+ on my wall-mounted rack.

Synology equipped the DS1520+ with a 2.0 GHz quad-core Intel Celeron J4125 CPU and 8 GB of non-ECC DDR4 memory. 

What’s interesting is that Synology decided to solder 4 GB of memory directly to the DiskStation’s logic board. That has led some people to believe that the second DIMM can be replaced and upgraded. Unfortunately, Synology confirmed that the DS1520+ doesn’t support more than 8 GB of memory.

Hardware Specification

You can see a full list of technical specifications here, but below are the ones that are most important to me:

  • Drive bays: Five (expandable to 15 using two DX517 expansion units)
  • Max storage (raw): 80 TB (expandable to 240 TB)
  • SSD cache: 2 M.2 NVMe SSD slots
  • Compatible drive types: 3.5” SATA HDD and 2.5” SATA HDD/SSD
  • Ethernet ports: Four gigabit with link aggregation/failover support
  • External ports: Two USB 3.0 and two eSATA

Based on my requirements and use cases, these are excellent specifications and there isn’t much more that I could ask for. However, I appreciate that some users may have wanted faster Ethernet ports with support for speeds of up to 10 Gbits per second, as well as more USB ports. 

Storage Capacity

Synology DS1520+ - Storage Manager - HDDs
I currently have five 4TB drives in my DS1520+.

You can equip this Synology DiskStation with up to five 16-terabyte hard disk drives for a total capacity of 80 TB. Additionally, you can add up to two DX517 expansion units to increase the full capacity to a whopping 240 TB. 

How much space you can use for your data depends on the type of RAID (Redundant Array of Independent Disks) you choose. A RAID 0 configuration would allow you to use all of your storage capacity, but at the cost of not providing any data protection in the case of a drive failure. On the other hand, a RAID 6 configuration would reduce the usable disk space from 80 to 48 TB, but it allows for up to two drives to fail before you lose data.

Regardless of how many HDDs you intend to use, keep in mind that a single volume can’t be larger than 108 TB. In other words, if you decide to install the expansion units and populate each slot with a 16 TB drive (240 TB in total), you’ll have to create three volumes to use all of that space effectively.

I have equipped my DS1520+ unit with four 4 TB drives and one 3 TB drive. I’ll replace the latter with another 4 TB disk as soon as I permanently decommission my LaCie RAID (which currently uses four 4 TB drives).

What’s cool about the DS1520+ is that it supports both regular spinning hard drives and solid-state disks (SSDs). The latter deliver much higher read and write speeds. While 3.5” spinning disks are available in capacities of up to 16 TB, I haven’t seen any SSDs larger than 4 TB. That means there’s a tradeoff between storage capacity and performance.

For my use cases, storage capacity was more important. That’s why I decided to use regular spinning disks. If you choose to go the SSD route, keep in mind that the bandwidth of your network will still limit the overall data throughput. 

Even if you aggregated all four Ethernet ports the DS1520+ offers, you’d only achieve a theoretical throughput of 4 GBit/s. That’s significantly lower than the speed of an average SSD.

The good news is that Synology added two expansion slots to the DS1520+, which you can populate with super-fast NVME cache modules. Doing so can speed up the read access significantly because the NAS can pull frequently-used files directly from the cache and without having to access the slower spinning disks.

RAID Configuration

Synology DS1520+ - Storage Manager - Volume
I decided to use an SHR configuration for my DS1520+.

Without going into too much detail about the different RAID configurations Synology supports, here’s an overview of all the supported types:

  • RAID 0, 1, 5, 6, 10
  • SHR, SHR-2
  • RAID F1

Two disk configurations you might not be familiar with are SHR and RAID F1. 

SHR stands for Synology Hybrid Raid, and its advantage is that you can get the benefits of a traditional RAID with the flexibility to combine disks of different sizes — something that most other RAID types don’t support. 

Additionally, SHR provides a one HDD redundancy and mimics the benefits of combining RAID 1 with RAID 5. SHR-2 provides a two HDD redundancy and mimics the benefits of RAID 6.

RAID F1 is a particular type of RAID you should use for disk arrays that contain only SSDs. The purpose of RAID F1 is to reduce the wear on your SSDs by continuously reallocating parity. The goal is to wear out each individual SSD at a different rate, so they don’t reach their end of life all at the same time. That could have disastrous consequences and lead to data loss.

When I set up my DS1520+, I decided to use the Synology Hybrid RAID. I did that because the role of my DS1520+ is to provide redundancy for my RS1219+. Even if two of the drives in the DS1520+ died and I lost all local data, I’d still have a copy of everything on my primary Synology NAS. In other words, I didn’t need double disk redundancy on the DS1520+.

If you use the DS1520+ as your primary storage solution, I highly recommend using SHR-2 so you can absorb the failure of up to two drives without losing any data. I also recommend having at least one new spare HDD around that you can hot-swap if one of the disks in the RAID stops working. 


Synology DS1520+ - Blackmagic Speed Test
Real-life performance tested with the Blackmagic app.

The following factors usually limit the performance of any NAS:

  • CPU
  • Disk throughput
  • File sharing protocol
  • Network speed
  • Type of RAID

I’d argue that the limiting factor in the DS1520+ is its network speed because it doesn’t support 10 Gbit Ethernet. The second factor is likely the Intel Celeron CPU.

To give you an idea of what kind of performance you can expect from the DS1520+, I’ve conducted speed tests based on the following configuration:

  • SHR based on Seagate IronWolf HDDs 
  • Apple Filing Protocol (AFP)
  • 1 GBit/s Ethernet

Using the Blackmagic app, I recorded write speeds of 60-75 MB/s and read speeds of 70-80 MB/s. That’s very reasonable, but about 30% slower than what I get with the RS1219+, which has a more powerful CPU and Seagate IronWolf Pro disks.

Ports and Interfaces

Synology DS1520+ - Back
There is an additional USB-A port on the front.

The DS1520+ has one USB 3.0 port on the front and one on the back, together with four Gigabit Ethernet and two eSATA ports. You can use either the USB or eSATA ports to plug in compatible devices, such as external drives or a printer. 

Just note that Synology doesn’t officially support connecting external drive enclosures with port multipliers. So you can’t connect a RAID enclosure to your Synology NAS. 

The only thing missing is an option to add a 10 GbE network interface card (NIC). That, combined with SSDs, could have improved the performance potential of the DS1520+ dramatically — assuming the CPU could handle it.

Synology DiskStation Manager (DSM)

Synology DS1520+ - DiskStation Manager
The web-based DSM is impressively responsive and easy to use.

Besides the slick hardware, what makes the DS1520+ such an attractive NAS solution is the software — and specifically, the Synology DSM. 

Before I got the DS1520+, I had no clue just how powerful and feature-rich the DSM was.

I won’t be able to get into all the features of the DSM as part of this review (there are simply too many), but I’d like to talk about the ones that I currently use. 

Folder Sharing

Synology DS1520+ - Shared Folders

Being able to access my data over the network was the primary reason why I got this NAS. To accomplish that, I created several shared folders and made them accessible over AFP and SAMBA. The latter I needed for my Final Cut Pro X projects because FCPX doesn’t support AFP.

Besides the two file sharing protocols I use, the DSM also supports NFS, FTP, TFTP, RSYNC and even iSCSI targets. 

DHCP Server

I use UniFi hardware from Ubiquiti to power my local area network (LAN) and to fulfill all of my routing and switching needs. 

Due to an issue in UniFi’s DHCP server implementation that causes intermittent connectivity problems with my IoT devices (such as HomeKit-enabled light switches), I decided to let my Synology NAS assume the role of the primary DHCP server for all of my LANs.

So far, that’s been working perfectly.

Interface Bonding with VLAN Support

Synology DS1520+ - Bonded Network Interface
You can bond two, three or all four interfaces for better LAN performance.

All of my Ethernet wiring uses CAT6a cables that are certified for frequencies of up to 500 MHz. As a result, these cables are capable of theoretical speeds of up to 10 Gbit/s. My iMac Pro has a 10 GbE NIC built-in as well, but the DS1520+ doesn’t. 

So I decided to bond all four of the DS1520+’s Ethernet interfaces to quadruple its network performance. 

What’s cool about Synology’s link aggregation feature is that you can connect the bonded interfaces to two different switches. I haven’t tested this, but I assume that if one of the switches becomes unavailable and goes offline, the NAS would still be reachable over the other switch.

In addition to interface bonding, I also needed to create several different VLANs to ensure the DHCP server would be accessible by all the devices in various (virtual) LAN segments.

Setting up one VLAN per interface is relatively straightforward because you can do it using Synology’s network control panel. However, if you need more than one VLAN per physical interface, you have to do it on the command line. 

If you’re struggling with setting up multiple VLANs on your Synology NAS, let me know in the comments and I’ll write up a step-by-step guide. 

Synology DS1520+ - Multiple VLANs
You can create multiple VLANs per physical interface on the command line.

But in a nutshell, here is how I did it:

  • Assign the primary VLAN to the NAS interface via Control Panel > Network > Network Interface > Edit (in my case, the primary VLAN ID was 10).
  • Log in to the NAS via SSH.
  • Navigate to /etc/sysconfig/network-scripts.
  • Copy ifcfg-bond0.10 to ifcfg-bond0.20 (assuming 10 is your primary VLAN ID and 20 is the secondary).
  • Edit ifcfg-bond0.20 and adjust the VLAN ID, IP address and netmask.
  • Save the file.
  • Restart the network stack via command /etc/rc.network restart.

Note that you might have to perform some of the steps above as a superuser (via the su command).

After restarting the network stack, you should see multiple copies of your physical network interface in the control panel — one for each VLAN ID.

Cloud Sync

Synology DS1520+ - Cloud Sync
Cloud Sync is one of my favorite features.

Before I migrated my data archive from LaCie to Synology, I used Backblaze to back up the data I had stored on both my LaCie RAID and my iMac Pro’s internal HDD to the (Backblaze) cloud. 

Given the huge amount of data — and to avoid delays or gaps in my backup — that meant keeping my iMac running, even while I wasn’t using it.

So one of my goals when migrating to Synology was to take my iMac out of the equation and have Synology directly back up the data from the NAS to the cloud. 

The way I accomplished that was by utilizing the Cloud Sync feature of the Synology DSM. 

Specifically, I enabled the following two services via Cloud Sync:

  • Backblaze B2
  • Dropbox

The Dropbox integration simply keeps a local copy of all of the data that I have stored in Dropbox. I already have a copy of that data on both my iMac and my MacBook Pro, but I figured it wouldn’t hurt to have an extra copy on the NAS as well.

If you have a Mac or PC with limited internal disk space, this feature could come in incredibly handy.

For example, my father-in-law used to have a MacBook Air with only 128 GB of internal disk space. But his Dropbox had much more than 128 GB of data. So he had to enable “selective sync” in the Dropbox app to selectively synchronize certain folders to his MacBook. If he had a Synology NAS with Cloud Sync enabled, he could easily access his entire Dropbox folder from the LAN without being limited by his MacBook’s available disk space.

The thing I am super excited about is the ability to sync all of my data directly with Backblaze B2. Unlike the consumer version of Backblaze, B2 is a low-cost cloud storage solution that’s ideal for backing up and archiving large amounts of data.

I’ve created two separate shared folders on my DiskStation. 

One is called Backup – Cloud. All of its contents get automatically replicated to the Backblaze cloud. This folder has all of the data that I can’t afford to lose.

The second folder is called Backup – Local. Its contents get locally replicated between my two Synology appliances. This folder contains the content of my Dropbox and other data that is either less critical or that I have stored in other cloud services.

Shared Folder Sync

Synology DS1520+ - Shared Folder Sync
The Shared Folder Sync features makes it easy to replicate folders between DiskStations.

As I mentioned before, my goal was to set up the DS1520+ as a copy of my RS1219+. To accomplish that, I use the Shared Folder Sync feature to automatically replicate all data from the RS1219+ to the DS1520+.

Under the hood, Synology uses the rsync protocol to automatically synchronize the contents of shared folders across the LAN (but you could also do that over the internet).

Setting up Shared Folder Sync was easy and involved the following steps:

  • Enable rsync on the DS1520+ via Control Panel > File Services > resync.
  • Create a synchronization task on the RS1219+ via Control Panel > Shared Folder Sync > Task List.

When creating the sync task, I could select what shared folders from the source (in my case the RS1219+) I wanted to sync and how often I needed the task to run. I picked “on modification.” That means that any time the contents of my shared folders change, the affected NAS immediately synchronizes those changes to the second unit.

Time Machine Backup

Synology DS1520+ - Time Machine
macOS automatically recognized my NAS as a backup target.

I haven’t used Apple’s TimeMachine feature in a long time, but decided to start using it again as part of my new backup strategy. 

Most of that strategy is geared towards avoiding data loss in case of a drive failure. While that’s important, it’s also vital to be able to restore older versions of files or folders if you accidentally overwrite them, or if ransomware encrypts your data (cryptojacking). 

That requires a solution that maintains a complete version history of all data and the ability to quickly restore individual files or folders.

The reasons I like Time Machine are that it’s baked into macOS and that it allows me to conveniently restore an older version of a file, if the need arises. 

The Synology DSM fully supports Apple’s Time Machine backups. That means you can create a special volume that Time Machine automatically recognizes as a potential backup destination during the setup process. 


The five-bay Synology DS1520+ without hard drives costs $700 on Amazon. In addition to the NAS, you have to factor in the cost of the disk drives. For example, five 4 TB Seagate IronWolf NAS drives would set you back another $500.

Check Price on Amazon

While that’s certainly a lot of money, I think it’s worth it if your requirements call for a network storage solution with all the bells and whistles the DS1520+ provides.

Other Interesting Features

Synology DS1520+ - Package Center
You can easily extend the feature set of your NAS via packages.

I have to admit that I’m only using a small fraction of the features the DS1520+ offers. It’s almost overwhelming how much this NAS can do. What makes the DS1520+ so versatile is Synology’s own app store, also known as package center.

The app store allows you to easily add new features to your Synology NAS by installing a new package. 

Below are some examples of features you can add to your DS1520+ via packages:

  • Central admin center for multiple Synology NAS devices
  • Network server (DNS, DHCP, CardDAV, Contacts, Email, Calendar, RADIUS)
  • iTunes server (to stream music stored on the NAS to any compatible iTunes or Apple Music client)
  • Media server (including Plex)
  • Video surveillance station
  • Virtual machine manager
  • VPN server
  • Web server (including support for Apache, PHP and WordPress)

The list of available native and third-party apps is nearly endless and I’m excited to explore more of those features in the future, especially the private cloud feature (Synology Drive) that could replace parts of my Dropbox and iCloud Drive.

Who Should Consider the Synology DS1520+

Synology DS1520+ - Drive bay
Being able to hot-swap bad drives reduces downtime and increases productivity.

The Synology DiskStation DS1520+ is an excellent choice for individuals and small businesses that demand a versatile data archiving, backup and storage solution to keep their data safe, even in the case of multiple drive failures.

In addition to power users like me, the DS1520+ can be a great solution for doctors’ offices, attorneys and similar small office environments and group settings that deal with a lot of documents and smaller files.

Besides leveraging the expandable storage capabilities of this NAS, these groups could also increase the return on their IT investment by leveraging the additional features Synology provides for free. 

For example, instead of paying for Dropbox or Google Drive, they could use Synology Drive. That not only saves money, but ensures that any sensitive data doesn’t get stored in a public cloud, which might violate data privacy regulations such as the Health Insurance Portability and Accountability Act (HIPAA), the Payment Card Industry Data Security Standard (PCI-DSS) and others.

However, I should mention that a Synology NAS might not be for everyone. For example, if you only want to back up a single device, such as your Mac or PC, and you don’t have any mission-critical data, an external hard drive paired with a backup solution like Time Machine or Acronis True Image might be sufficient.

In such cases you could even add a cloud-software backup solution like Backblaze to maintain an off-site backup in case both your computer and your external backup drive fail.

On the other end of the spectrum are professional users, such as videographers, who need fast storage that can handle massive amounts of data. Considering that the DS1520+ doesn’t have a 10Gbe network port, you won’t get the required data transfer speeds you might need to edit a 4K Final Cut Pro X project that is stored on the NAS (for example).

Frequently Asked Questions

What’s the difference between an NAS and a DAS?

NAS is network-attached storage, such as the DS1520+, whereas DAS stands for directly-attached (via USB, Thunderbolt, eSATA, etc.) storage. A regular external hard drive or the LaCie 5g Thunderbolt are DAS devices.

As a rule of thumb, directly-attached storage is usually faster because USB 3, Thunderbolt or eSATA offer higher speeds than standard (1Gbe) ethernet links.

Can I access my Synology NAS from the internet?

Yes, you certainly can — by either configuring port forwarding on your router or by using what Synology calls QuickConnect, a feature that enables you to access your NAS from the internet without having to worry about configuring port forwarding on your router.

You can enable QuickConnect using the Control Panel of the DSM.

Can I upgrade the DS1520+ to 10 GB Ethernet?

Unfortunately, the DS1520+ doesn’t support extension cards. All you can do to improve the network performance is aggregate the four 1Gbe ports.

Can I upgrade the memory of the DS1520+?

You cannot upgrade the memory in the DS1520+ because it already ships with the maximum memory configuration the hardware supports. 

What’s the difference between the DS1520+ and the DS1519+?

The DS1520+ is the successor to the now-obsolete DS1519+ and features improved hardware specifications that result in better overall performance. According to Synology, the DS1520+ is almost 14% faster in file indexing and almost 20% faster application performance, thanks to the upgraded CPU.

It’s also worth noting that the DS1519+ had only two LAN ports and only one eSATA port, and it supported only a single expansion unit.

What file systems does the DS1520+ support?

You can format internal drives with Btrfs (recommended) or EXT4. External drives can be formatted with Btrfs, EXT3, EXT4, FAT, NTFS, HFS+ or exFAT. The latter requires the purchase of an add-on package.


It’s been a few weeks since I deployed the DS1520+ NAS and every time I log into the DSM, I’m still amazed by how feature-rich the platform is.

But it’s not only the software that makes Synology an excellent storage solution. The hardware is top-notch as well. The NAS enclosure looks and feels premium and you barely notice the fan spinning (although you can turn up the fan speed if ventilation is an issue in your environment).

From a performance perspective, I have absolutely nothing to complain about. I know that the DS1520+ is not the most performant NAS Synology has in its lineup, but unless you require 10 Gb Ethernet, I doubt it will result in a bottleneck. 

I use the DS1520+ as a means to maintain a backup copy of all the data I have stored on my RS1219+ and all of that data replication happens in the background.

As a result, the raw speed of the data replication process isn’t a major concern for me. 

Overall, I’m convinced that the DS1520+ is an excellent choice for all users who are looking for a data storage solution that’s easy to install, that provides superior data protection in case of hardware failure, and that can grow with your data. 

I wish that I had made the jump to Synology much sooner; I don’t know what took me so long.

8 thoughts on “Synology DS1520+ DiskStation Review”

  1. Did the RAID volumes take a long time to build? Was it a matter of minutes or was it hours to build and format and did it matter about the size of volumes or type of RAID used as to how long it took?

  2. Hey Mike,

    I was very skeptical about upgrading the synology DS1520+ to more than 8GB RAM. As stated from intel website, the onboard can support upto max 8GB RAM. But I see alot of people successfully upgraded more than 8GB RAM. I personally tested my friend’s DS1520+ with my 16GB spare DDR4 (TimeTec brand), and it works. DS1520+ is able to see 20GB RAM. Synology bootup without any issue. Now I’m also planning to get one since I’ve tested DS1520+ is able to support beyond 8GB RAM

  3. Looked at doing the multiple vLans on my DS1821+ but when you create the bond the files are different. Its now called ifcfg-ovs_bond0 . Wondering have synology changed something ?

    • Not sure. They are still called:


      On my system.

  4. Hello, reading your post has helped out a lot in deciding to buy the DS1520+. I want to buy 5 disks maybe 12TB each. I run a virtual machine using Hyper-V on Windows 10pro.
    Would having the virtual machine on the NAS drive work good for speed. I would also combine the 4 Ethernet ports like you have, i would need to buy a managed switch to do this? My current PC XPS8940 new this year and i love it. i also have an old Mac book pro 2009 (yes it works great, with some updates RAM and SSD). so the feature for time machine is good to. Anyway any advise would be much appreciated.
    many thanks

    • Hi Richard,

      I think the DS1520+ should be fast enough to run a virtual machine, unless you perform a lot of disk-intensive tasks on it. That said, I’ve never done that, so I’m just speculating :)



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