If you've read one of my NAS reviews in the past, you'll know that I'm a big fan of managing your own data. Cloud services are great and definitely have their place in the world, but I prefer to be in control of my own files and use cloud services more as a second backup or a way to quickly share pictures with friends and family.

Today I'm going to take a look at the latest offering by Synology, the DS720+, a two-bay NAS device that can be expanded with the Synology DX517 to a seven bay unit.

Specifications

Upon initial inspection, the DS720+ looks like all of the other 2-bay NAS devices Synology has released over the past few years. One of the big differences is the fact that they included two NVMe slots on the bottom, to be used as a read or read/write cache. If you're interested in the results, you can scroll directly down to the Cache Performance section.

Synology always packs the most powerful hardware in the + line, and the DS720+ is no exception. The device sports a quad-core 2.0 GHz (2.7 GHz burst) Intel Celeron J4125 processor with on-chip AES-NI encryption and 2GB of DDR4 RAM (upgradeable to 6GB). The processor was released at the end of 2019, and you can see the details on Intel's website.

There's a single 92mm system fan in the back to keep the DS720+ cool, and it's very quiet so it won't be distracting in a home office setting.

CPU Intel Celeron J4125, quad core, 64-bit, 2.0Ghz with AES-NI encryption
Memory

2 GB DDR4 non-ECC, one empty slot (6GB total)

Disk Capacity

32 TB (16 TB drive x 2) without expansion, 112 TB (32 TB + 16 TB drive x 5 with DX517) (hot swappable)

Network 2xGbE (with link aggregation/failover)
USB Ports 1xUSB3 (back), 1xUSB3 (front)
NVMe Slots 2 (bottom)
Size (H/W/D)

6.5 in x 4.2 in x 8.8in (166 mm x 106 mm x 223 mm)

Weight 3.3 lbs / 1.51kg

From a connectivity perspective, there are two Gigabit Ethernet ports on the back that can be aggregated into one to improve performance. Note that you can't double your throughput from a single stream, but rather the aggregation can be used as either failover in case a switch port dies, or can be used to improve bandwidth on multiple streams.

The DS720+ has two USB 3.0 ports, one on the front and one on the back, although the "copy to NAS" button has been removed from recent Synology models.

If, in the future, you decide you need more than two drive bays, there's an eSATA port that allows you to add storage space via a Synology expansion unit. You can also secure the DS720+ with a Kensington lock if you're concerned about the physical security of the device.

The device also supports up to two M.2 NVMe SSD chips, accessible via the bottom of the device. If installed, these are used purely for caching and can't be added to your overall storage usage.

Hardware Installation

If you're looking for something that's plug and play, you can't go wrong with Synology devices. To get them up and running, simply connect the disks to the sleds, and plug them into the front drive bays. Then plug in an Ethernet cable, plug the power cable in, and then turn the device on. The system will boot up, obtain an address via DHCP, and you can connect to begin the installation process.

If you want to build the cache, installing the NVMe drives is as easy as turning the DS720+ over, opening the drive bays, and sliding the chip into place. I didn't put a heat sink on the Western Digital Black drive, and while temperatures were about 7ºF/4ºC higher than the internal drives, there were no thermal performance issues, even under load.

Initial Setup and Installation

Setting up the Synology DS720+, or any Synology NAS device for that matter, is as easy as clicking a few buttons and can be done in only a few minutes.

If this is your first Synology device, I would recommend downloading the Synology Assistant for the initial setup. Install this tool on your desktop and it identifies all of the Synology devices on your network so that you can just click on them to connect. While you could look at your DHCP server to find out what IP address it assigned, this just makes life easier.

When you first connect to the Synology DS720+ from your browser, you're presented with the Web Assistant page that begins the setup process.

After that, you're given a screen that begins the installation of Synology DiskStation Manager (DSM) onto the NAS device.

As is typical for any destructive process, the system warns you that all data on the hard drives will be destroyed, and you must acknowledge this before you may proceed.

The installation then begins. Although the process says it takes approximately ten minutes, if you have a fast Internet connection, it shouldn't take quite that long.

Once DSM is installed, it's time to setup the actual operating system. The system prompts you to give the NAS device a name, and to create a username/password combination that will act as the admin account on the DS720+.

Next, you're asked if you want to setup QuickConnect, a feature that gives you access to your NAS device from the Internet, in essence providing you with a public cloud. If you want the best security, you can skip this feature. If you want easy access to your files from the Internet, you can enable QuickConnect, just make sure you turn automatic updates on to help limit damage from attacks against your device.

On the next screen, you're given the option to share the device's network location so that you can identify it on the Internet.

That's it, your Synology DS720+ is now configured and ready to use. However just because the operating system is installed, doesn't mean you can actually do anything with the device yet, since you haven't actually configured the storage. This is one area where I think Synology could improve the initial setup. If you have a storage background, the rest of the setup is straight forward, but for those who don't, it may not initially make sense.

Initially, Storage Manager will show that you have a healthy system, but that you have no volumes or pools, only two drives. The configuration steps are simple: Create a Storage Pool, a Volume, and then finally Shared Folders.

Let's start by creating the Storage Pool. Think of this as a conglomeration of all of your disks into one big blob, and is where you configure what type of disk protection you'll have to survive disk failures. Select the "Quick" installation, since with only two disks in the NAS, there's little reason to go for the Custom configuration.

Next, give the pool a descriptive name and select the RAID type; for a two-bay NAS, I'd always recommend SHR, as that gives you protection from a single disk failure. If you select RAID-0, you'll have twice the storage space, but when a single disk dies, you'll lose the data from both disks, so it's only recommended for special circumstances.

Creating a new volume destroys the data on the drives, so you'll be prompted to confirm the procedure, before being asked to select a filesystem type. There are two choices, Btrfs and ext4. Unless you have a need to remove the disks and mount them on a Linux server or an older Synology NAS device in the future, I'd recommend sticking with the default of Btrfs.

Once the volume and filesystem are created, it'll take many hours, depending on the size of the disks, to run an integrity check against the disks. You're still able to use the DS720+ while this is happening, but performance will be degraded.

Now all that's left to do is create whatever Shared Folders you want on the system. These are used to create different characteristics for different shares that you'll be accessing on other machines in the environment. For example, you might have one share that has disk-level encryption enabled, while another has data integrity enabled, and a third has the concept of a Recycle Bin turned on.

Start by loading File Station, and you'll be prompted that there are no Shared Folders available. Click "OK" to go to the Shared Folder Creation Wizard.

You're then taken to first menu of options. You'll need to give the folder a name, and then decide if you want it hidden from "My Network Places" on the network, whether you want to hide sub-folders and files if users don't have permissions to access them, and whether you want a Recycle Bin enabled.

The next screen asks whether you want to encrypt the folder. Doing so will add security to the data, but whenever the DS720+ reboots, you'll have to manually use the key to mount it, or use the Key Manager tool. Key management is a topic I'll look to address in a future article.

Your last decisions are whether you want to enable data checksums to improve data integrity, if you want file compression enabled (only if checksum is enabled) to reduce storage at the cost of performance, and if you want to enable a quota on the folder. I'll cover this in the Performance section, but during my tests, CrystalDiskMark write performance doubled in the Random 4k Q32T16 test, and the other tests were the same, so there appears to be little reason to disable the checksum option.

Once created, you'll be able to mount the disks onto whatever other systems you want on your network.

If you want to mount storage on only a single device, you might want to look into creating an iSCSI LUN to share. This is especially useful if you're using the Synology DS720+ as storage for a VMware or Hyper-V system.

Performance

As with all of my NAS reviews, in order to test performance and bypass the PC as much as possible, I used OSFMount to create a 4GB RAM disk and then used Robocopy to test throughput between my desktop and the DS720+. The volume on the NAS was created as SHR using the Btrfs filesystem. This is similar to a RAID-1, since there's only two drives. In addition to the above method, I also used CrystalDiskMark 7.0.0 x64 to run some tests to confirm that the performance matched what I was seeing with the manual tests, which they did.

For my test, I created five separate shared folders, each one configured slightly differently in order to see how certain features would impact performance. The tests included:

  • A regular filesystem
  • A filesystem with integrity enabled
  • A filesystem with integrity and compression enabled
  • A filesystem with encryption enabled
  • A filesystem with encryption and integrity enabled

As you'll see from the results, performance was consistently at or near gigabit Ethernet speeds when sending large files, but when reading and writing smaller files, the performance changed quite a bit depending on the filesystem.

The first thing I noticed during my tests was that performance was nearly the same between a regular filesystem and one with integrity checking enabled, except for one test: the RND4K Q32T16 write test performance was nearly double with integrity enabled. I'm not sure how real-world a queue depth of 32 is on the 4K block test, but since everything else is nearly the same, there appears to be no reason to leave integrity disabled on the filesystem.

The piece that surprised me a bit was that performance remained relatively unchanged when integrity and compression were both enabled; I would've expected there to be a slight performance hit with the compression from a read perspective, but the DS720+ experienced no slowdowns both with the CrystalDiskMark test, and with real-world file copy tests. While you should certainly do your own tests to make sure there's no impact with your workflow, it seems like there's no reason to not enable both filesystem integrity and compression for normal workloads.

Next, I tested a filesystem with encryption enabled and one with integrity and encryption enabled. I saw the same performance boost in the RND 4K Q32T16 write test, going from 33 MB/s without integrity enabled to 67.98 MB/s with integrity enabled. While this value was slightly lower than the filesystem with only integrity enabled, it wasn't too big of a hit.

However the pain came for both the reading and writing of random 4K blocks with a queue depth of only one: As you can see above, the read rate plummeted to only 8 MB/s, compared to 16 MB/s without encryption. Even worse, the random 4K blocks with a queue depth of 32 nosedived from gigabit Ethernet speeds (116 MB/s) down to a paltry 12.5 MB/s. Although the DS720+ has hardware encryption built in, if you care about performance over security, this is not a feature I recommend taking advantage of on the filesystem.

Cache Performance

The DS720+ has two empty NVMe slots at the bottom of the device if you want to use cache to improve performance. Using one drive will improve the read cache, while installing two will improve both the read and write cache. One thing to note is that every 1GB of cache will use 416KB of memory. Installing my Western Digital Black 512GB chip utilizes 188.9MB of memory, or roughly 10% of the total system memory of my test unit.

I installed a single Western Digital SN750 500GB Black drive into one of the NVMe slots in order to test the performance of the system's read cache. Installation was simple, taking no more than a couple minutes to complete.

After the installation, boot up the DS720+, open up Storage Manager, and click the SSD Cache Advisor at the top see information on recently accessed files and what the recommended cache size should be for your system.

Creating the cache is simple. To start, click the Create button at the top of the SSD Cache section of Storage Manager, then select whether you want a read-only cache or a read-write cache. Note that in order to create the latter, you need to install two NVMe drives into the system.

Next, you're asked to select which SSD you want to use for the cache. With only one drive installed, the selection options are pretty straight forward.

Finally, you're asked how much space on the drive you want to allocate to the cache. If you're going through the trouble of creating a cache, you should probably select all of it, unless you're really short on memory.

Now whenever you're on the SSD Cache tab of Storage Manager, you're presented with a cache usage monitor that displays the hit rate over the past day, week, and month, as well as how much of the cache is being utilized.

While setting up the cache is simple, I can't recommend it for normal home users. Running a CrystalDiskMark test on a filesystem with integrity enabled showed no change in performance with the cache. Thinking it was due to the random nature of the data being written, I began copying the same files to multiple different filesystems and again noticed no difference. While caching might improve performance in a small business environment with multiple people using it consistently on a daily basis, if you're using it for a home setup, it doesn't seem like it makes sense.

Conclusion

The DS720+ is a great device, but recommending it will depend on the individual's use case. If you're in the market for a small NAS device to backup your files, and that has the ability to grow, the DS720+ is a great device to purchase. It provides great performance, takes up little space, and is on the whole, very quiet. If, down the road, you need more space, you could always purchase a DX517 expansion module, but that can be an expensive option.

On the other hand, if you think you might need more storage space in the future, you probably want to look at the DS420+, which has four bays, and costs only $100 more. Running in RAID-5 or SHR configuration, you would have three drives worth of storage space, as opposed to just one in the DS720+ (assuming mirroring). If you need video transcoding in addition to more space, at this point the older DS1019+ might also be a better option.

The two NVMe slots for caching are a nice feature, but during my tests, offered little in the way of performance in a small home setup, so that shouldn't factor into your decision.

Considering the maturity of both the Synology hardware devices and the DiskStation Manager operating system, if you're in the market for a two bay NAS device, it's easy recommend the Synology DS720+.

 

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