Selecting a Synology NAS

Posted Thursday, April 21, 2022 by Sri. Tagged REVIEW
EDITING PHASE:first draft

My current cheap-o NAS, a 3TB WD MyCloud, has entered end-of-life and needs replacement anyway. I decided to buy a new NAS from Synology, as they have been in the NAS game for a long time AND are a Taiwanese company. QNAP is also a Taiwanese company, but they haven't been doing it for as long. Synology gets recommmended all the time also, so why not start with them?

Synology makes a lot of different NAS products and releases a new set of model numbers periodically for different use cases. The latest models as the various DS*20 (e.g. DS220, which has two bays and was released in 2020) and can have various suffixes like +, j, play, and so forth. This is my selection process to pick the right NAS for my needs (with some wriggle room to get something cool).

I went with the Synology DS-720+ because although it was overkill, it was only $99 more than the 'sized-right' without cacheing and two fewer processing cores.


My critical application is backing up digital photo raw files, which can be quite large. There are thousands of discrete files too, with hundreds of files in folders. Although it is not recommended, I actually store my raw photo inputs directly to my current NASthing, an ancient single-drive Western Digital MyCloud (purchased 2014) and then process over the network with Lightroom. It's pretty slow. The MyCloud backs itself up to an external HD. I'd like to get my data transferred off it.

So, tech specs I think I NEED:

  • decent throughput...current network is switched gigabit, which has a theoretical max throughout of about 125MB/sec but is likely lower than that.
  • Most hard drives I'm pricing in the $100 range have greater than 125MB/sec read/write throughput, so I don't think I need to have a RAID setup for a NAS to max out speed.
  • Bandwidth aside, making sure the NAS can keep that bandwidth filled means I need enough memory and cpu to manage file indexing to feed the network. The typical max load would be three computers, one reading files and another writing during a large backup of files, with all other devices needing to also access the drive perhaps while this is going on.
  • Ability to back up to remote sites AND easily restore!
  • 4TB of storage has historically been more than adequate for me. I'm using around 2.5TB right now for photos + music.

Things that would be nice:

  • having hot swappable drives, or having 4 bays might be nice for updating drives as they age out, without having to replace smaller drives. I could probably get away with a 2-bay unit since offsite backup through Backblaze or is what provides redundancy.
  • media serving would be kind of neat, but in practice I don't think I would use it
  • remote access I don't think I need
  • mail server built-in, collaborative sharing of docs, etc...don't need it.
  • media encoding from IP cameras sounds cool...but likely don't need that either.
  1. I think what I am looking for is a box with a modest but symmetric throughput around 115-125MB/s...anything more than that would just be choked by the gigabit ethernet.

  2. I am more concerned about random file read/write speeds, so the box should be able to handle this as well as it can. Capable high-IPC multi-threaded processors and enough memory to handle big lists of files, perhaps compressing them on-the-fly, able to service at least two clients writing/reading as hard as they an while allowing another client to still access files without getting locked out...

  3. Synology boxes seem to have a lot of integrations for remote backup services so I don't think that is as much as a concern.


Let's start with basic price and number of bays


bays, price (diskless) on amazon

DS220j  2-bay  $200*
DS218   2-bay  $249
DS418   4-bay  $370*
DS220+  2-bay  $299
DS420+  4-bay  $499
DS720+  2-bay  $399
DS920+  4-bay  $549

* These are out of stock on amazon, so using historical price from camelcamelcamel.


  • The J series is entry level.
  • The DS*18 models are 2018 models
  • The + models are ones that are enhanced somehow



DS220j  4c1296,  512MB
DS218   4c1296,  2GB
DS418   4c1296,  2GB
DS220+  2cJ4025, 2-6GB
DS420+  2cJ4025, 2-6GB
DS720+  4cJ4125, 2-6GB
DS920+  4cJ4125, 4-8GB

cpumark, single core
ARM 1296 -  425/ 184
Cel 4025 - 1688/1234
Cel 4125 - 3000/1173

The ARM processors look particularly weak, so dropping them except for the DS218 (which also has 2GB matching the base config of the celeron models)


max read/write speed

DS218   112/112
DS220+  225/192
DS420+  225/225
DS720+  225/225
DS920+  225/225

All the choices are meet or exceed the gigabyte ethernet throughput. However, the plus models achieve double the rate because it has TWO gigabit ethernet ports. I'm not doing link aggregation (?) so this doesn't add-up to anything useful for me.


workflow crunching speed! hard to estimate, but we can look at video encoding and limits to get a sense of relative similarity using H265 3MPIX encoding:

DS218   240
DS220+  500
DS420+  500
DS720+  600
DS920+  1000

Interestingly at 4K we see a drop in the 720+ below the 220+ and 420+. This might be a typo, or maybe it indicates an architectural difference.

The 220+ and 420+ are approximately the same in media encoding strength and use the same 2-core celeron 4025. The 720+ and 920+ use the 4-core celeron 4125.


other considerations?

  • The 220+ looks like it exceeds my specs a bit and would serve my current needs just fine.
  • The 420+ has some advantages: additional bays for presumably easier swapping-in of drives when it's time to retire them, but I'm not sure if it actually works that way. Easier to add more capacity though as I need it, IF I need it. Perhaps there are ways of mapping certain directories to certain volumes, which would help optimize simultaneous read/write operations?
  • The other difference with the 420+ is that it has slots for NVME ssd drives for cache. This might make read/write speeds much more consistent in backup operations or using a file over the network, particularly when the NAS is under load. But that might be unlikely.


  • The DS220+ is $299
  • The DS420+ is $499

A starter Hitachi Deskstar 6TB drive is about $80 currently.

I'm leaning toward the 220+ though it would be cool to have the caching. In practical use, though, as I rarely edit large raw files. From some prelinary reading on how the cache is used, I don't think I see a 40% increase in speed for the 40% increase in price. If I worked directly off the network I would, but I never do that!


They don't get that much cheaper with the 2-bay options, and the cheaper 4-core ARM CPU looks like it has about 1/4 of the processing power of the Celeron 4025 even with half the cores.

Looking at the notes in sites like NASCOMPARES, the faster CPUs deliver fewer "hiccups". The sweet spot probably is the 220+?

Here's a handy model number guide I found on windows central

  • se - Budget-friendly option.
  • j - Affordable option for home use.
  • play - Usually has a more powerful processor for better transcoding.
  • + - Sports an Intel processor.
  • +II - The same model as the "+" but with a newer processor.

Using the list above, it's easy to see which of the DS218 range you'll be best suited with. (The DS218 is essentially the model year and the number of bays. DS216 would be a two-bay unit from 2016.) A DS218+II would be a DiskStation NAS with a newer generation of Intel processor.

Now reading reviews on the 220+, and learning a bit about link aggregation and how it might work.

Some additional thoughts:

  • While the base transfer read/write speed of a single HD theoretically can keep up with gigabit ethernet, in practice the latency due to random access seeks will kill performance when dealing with lots of tiny files (pretty typical with my media storage). Probably not much I can do about that unless I spend a lot more money. I can just wait longer, I guess. I very rarely use the NAS for anything but backup and long-term storage.

  • I just realized that the DS720+ is just $99 more, but has the more powerful processor AND the option for SSD cache in separate slotsl


The DS720+ 2-bay NAS at $399 has the higher-end 4-core intel processor, expandable RAM, and the extra cache slots for an NVMe drive. Overall, these would help the NAS handle the large file transfers and simultaneous read/write better than a lower-powered NAS. I am willing to pay for speed.

The MyCloud was a bit sluggish at a lot of operations. For comparison, my 2016-era MyCoud is said to have the following specs:

Mindspeed Comcerto 2000 (M86261G-12) dual-core ARM Cortex-A9 at 650MHz
256 megabytes of Samsung K4B2G1646E DDR3 RAM

Even the cheapest NAS has is running a 4-core RTK1296 (ARM Cortex-A53), 512MB. The A53 supports 64-bit operation and uses the ARMv8-A architecture, while the A9 uses the ARMv7-A architetecture. Speedwise it's hard to find a benchmark...from the raw specs I might surmise they aren't that different in speed, but are instead optimized for power consumption and efficiency. Still, the A53 has approximately twice the clock speed and twice as many cores, so we might expect a significant improvement. But even then, the Celeron 4-core solution is much faster though uses more power.