Chapter 01 - Synology Hardware

Deciphering the Model Numbers

With over 30 NAS models Synology’s product list can be daunting at first glance. But the model number will help you zero in on the models that will meet your needs.

Synology product list from June 2015

Synology product list from June 2015

The model numbers begin with two letters which identifies the type of NAS. Although there are six prefixes in the table below, the vast majority of the models are DS and RS versions. The EDS and VS models are special cases and the DX and RX prefixes are for expansion units, not standalone NAS units.

Synology NAS Prefixes
Prefix Description
DS DiskStation: designed to sit on a table or shelf. These models run the gamut from home to enterprise use.
RS RackStation: designed to fit into standard 19“ computer racks used in data centers. Generally these are more powerful than the comparable DS model with more technology and are more expensive. |
|DX | DiskStation Expansion Unit: expansion unit to add drives to the DS NAS model. These expansion units are designed to sit on a desk or shelf. |
|RX | RackStation Expansion Unit: Expansion unit to add drives to the RS NAS models. These expansion units fit in a standard 19” computer rack.
EDS Embedded DiskStation: designed to be used in a harsh or specialized environment. There’s no internal drives and everything must be external. The DSM software is pre-installed. These are designed for cars, boats and other specialized environments.
VS Surveillance Station: (aka Video Station) This is a companion device for managing live feeds from security cameras. There’s no internal disk and it must be paired with a Synology NAS.

While the EDS and VS units do run the same DSM software they are for specialized use and this guide will not address the differences in these models. Also, the model naming convention I’m about to describe doesn’t apply to these EDS, VS, DX and RX models.

After the prefix there are three or four numbers. These identify the maximum number of drives that the NAS can manage along with the model year. If there are three numbers then the first number is the number of drives that the model can manage. If there are four numbers then the first 2 numbers are the number of drives that the model can manage. The total number of drives doesn’t mean that the model has that many drive bays, many models support expansion units (DX and RX units) and this number includes the maximum number drives, including expansion units, that are supported.

The next two (or last two) numbers are the model year of the NAS. Like cars, the model year starts updating before the actual calendar year. For example, the DS415+ is an update of the DS412+ and it was released mid–2014 and widely available that November. Unlike cars, Synology will not upgrade each model line each year.

Synology refers to the year identifier as the series. For example, the DS1511+ is part of the 11-series.

After the numbers there’s a model performance category identifier suffix. The identifiers are:

Synology NAS Suffixes
Class Suffix Description
j This is the entry level “budget” model for the series. Lower power and lower price.
No Suffix These are the standard models for the series. Middle of the road in performance and price.
+ These are the high performance models for the series. Highest in price and performance. Synology considers these business models.
xs These are enterprise class models that have enterprise features and prices.
xs+ Also enterprise class models but with more power, features, and cost than their xs siblings.
RP This means the model has redundant power supplies. The model will include other class suffixes.
play A specialized model that is enhanced for video streaming.
slim A specialized model that takes up less space but can only be used with 2.5" drives.
se A specialized low cost, entry level model. It is less capable than other models in the series.
air A model with a wireless card built in. It can be used to connect to the LAN, server as a wireless hotspot or as a router.

While the same Synology software runs on all models, this guide will only cover the first three classes. The specialized features of the other classes won’t be covered.


Hardware warranties range from two to five years. Consumer and small business models (which is most of them) have a two year warranty. Medium to large business models, which are ones that support expansion units, have a three year warranty. Enterprise (xs and xs+) models have a five year warranty. It comes as no surprise that the warranty length increases as the price increases. (These are rules of thumb for the warranties, always verify the warranty before buying your NAS.)

Software Support

Synology will provide major firmware updates for about five years after a models release. Although after three years updates may be slower in coming and may eventually be limited to security updates and bug fixes. Synology may consider a “dot” release to be a major update. For example, when Synology moved from DSM 5.0 to DSM 5.1 they did not release new firmware for some older x10 models until a couple months after it’s initial release. Synology has one major DSM release per year so while DSM 5.0 to 5.1 may seem like a small “dot” upgrade, it was a year after the DSM 5.0 release and Synology considers it a major release.

These are not official Synology policies as Synology does not have an official policy or guarantee for firmware updates. They are based upon Synology’s recent practices. I would consider three years a conservative estimate for how long you should expect new features in your firmware updates and five years a reasonable estimate for security updates.

Synology has announced that DSM 5.2, released in May 2015, will be the last major DSM version support by the 10-series models.

Picking Your Synology Model

If you’re considering an enterprise model, the surveillance station or the embedded DiskStation then this section isn’t for you. If your looking for more general home or business use then read on.

When deciding on your Synology NAS think about the following:

  1. What is your budget?
  2. What will you use Synology for? (File storage, running applications/packages, backup of other computers.)
  3. How much disk space will you need?

The Short Answer

I really like the DS415+ and DS214+ models, or whatever the current model in the DS4xx+ and DS2xx+ series are. The DS415+ really towers above other models in bang for the buck. It’s become my most recommended NAS.

For maximum expandability and flexibility, without getting into rack mounted or enterprise models, either the DS1513+ or DS1815+(or latest DS15xx+ or DS18xx+ series models) are excellent choices. They have 5 (DS15xx+) or 8 (DS18xx+) drive bays and can add another 10 drives with the addition of two expansion units. This flexibility does come at a price (in dollars). I have used a DS1511+ for a couple years and it has served me well.

One thing these recommendations all have in common is that they are all + (plus) models. The + (plus) models provide extra power to run applications so they’re ready for expansion as your needs grow.

1. What’s Your Budget?

This is fairly straight-forward although you may want to reword this as “how much am I willing to spend?” Don’t then immediately go to the largest model you can afford, but if you have some extra money after reviewing the next two points you may want to consider stepping up to one with a better warranty and to allow for future expansion. Or you may simply decide to be a savvy shopper and save money.

2. What will you use the Synology for?

This is one of the potentially more complicated questions since a Synology NAS can do so much.

File Storage

The most common use of a NAS is to to store files. I have two active Synology NASs myself. One is used as my primary file storage, meaning the files I access and use on a regular basis. A second NAS is used as secondary storage, meaning archives and backups.

Will your Synology be used for primary storage, where everyone in your family or business can access the files? Will it be used for secondary storage - archiving and backup of your computer files with infrequent access? Or will it be used for both? Having two copies of your files on the same NAS is not a good choice as a backup solution, so by “both” I mean primary storage for some files and archive/backup for a separate set of files.

If you’ll be doing video or music streaming you should consider these files part of primary storage since you’ll want quick access.

Determining your disk space needs is covered in more detail in the Capacity Planning chapter.

The difference:
Primary storage: If you’ll be using the NAS for primary storage and will be accessing the files frequently you should skip the lower powered “J” models. An exception to the “J” exclusion is if only one person will be using the Synology, or at most one person at a time, and you’ve got a limited budget,

Secondary storage: If you’ll be using the NAS for secondary storage you’ll probably be less concerned about speedy file access. A “J” model may be suitable for you.

Video Streaming

If you’ll be using your NAS for video streaming you’ll want a little more power or you’ll want a NAS customized for video streaming.

I generally recommend more power over video customization since the power can benefit all the ways you use your Synology. But if your primary use will be video streaming and maybe a little backup file storage then the “play” models are worth a look.

I would recommend avoiding the “J” models for video streaming unless your usage will be very light and you have a limited budget.

Music Streaming

Streaming music is not a very intensive operation. It’s demand on the NAS is comparable to a constant file copy so this doesn’t affect your decision beyond the storage needs for your music and how many people will be accessing the music at one time.

BitTorrent or other file downloading

Download Station can be used to download BitTorrent and other large files. If you’ll be doing this constantly, and use other applications at the same time you’ll want to avoid the “J” models. If your primary use will be for BitTorrent then you can use the “J” model since Download Station itself isn’t very intensive.

Other Applications

There’s so many applications available for Synology it’s impossible to list them all here. But if you expect to run multiple applications at the same time you’ll want a + (plus) model since these are designed to have the extra memory and horsepower needed to run multiple applications.

Multiple Users

If you have multiple people who will be accessing the Synology NAS at the same time you’ll want to avoid a “J” model.

You may also want to consider a model that supports Link Aggregation. This means that the network traffic can take advantage of multiple network cards. But to do this you’ll also need a network switch that supports Link Aggregation. Typically, home routers that include built-in network ports do not support Link Aggregation so you’ll need to buy a network switch. I currently use a TP-LINK TL-SG2216 16-Port Gigabit Smart Switch, although there are many other options.

Note: DSM 5.2 added network load balancing which provides many of the benefits of link aggregation without requiring special network hardware. I haven’t used this enough to know how beneficial it is, but it does seem promising.

Picking The Right Hard Drives

Spinning Drive (HDD) or Solid State Drive (SSD)

Spinning Drives (HDDs) provide the most storage space for the buck. Solid State Drives (SSDs) provide much faster performance. The price of SSDs is also dropping. While they are still much more expensive per GB than a spinning drive, the cost is within reach for many people.

While there are exceptions, drive speed is not going to be the limiting factor in most home or small business setups so the added cost of an SSD will be wasted money. Once of the exceptions is if the NAS is running several applications which are being accesses by many users at the same time and they expect fast responses. Unless you have special requirements and design your NAS and network for performance you will not benefit from an SSD[1].

Pick any hard drive brand and you’ll find it has it’s opponents and proponents. There’s also been a lot of consolidation in the hard drive industry. Western Digital and Seagate are the big players in the industry. Toshiba is a distant third. Hitachi, a popular brand, was bought by Western Digital but some of it’s business was sold to Toshiba to win regulatory approval. So what does all this mean to you? Nothing, except the brand doesn’t really matter so don’t worry about it[2].

The primary factor in picking hard drive is verifying that it is on Synology’s compatibility list. Be sure to check the notes for any exclusions or limitations. I have used drives that weren’t on the list (especially in the early days of SSDs) but only when I was doing testing and didn’t want to buy drives. While I didn’t have any problems, your data (and time) are too valuable to risk on untested drives just to save a couple of bucks. I never used with data I was unwilling to lose.

NAS’s are always on, so the drives are spinning a lot. (Unless you plan to sleep or power down the NAS when it’s not in use.) Because of this you’ll want to avoid drives promoted as desktop class, even if they’re on the compatibility list. Or, if you do use desktop class drives have a spare ready to swap in. If the drive fails in the warranty period you’ll be able to send it in for replacement.

A recent development are drives promoted as “NAS drives”. These are typically less expensive than enterprise drives, but slightly more expensive than desktop class drives. Western Digital markets these as “Red” drives while Seagate uses the unimaginative “NAS” moniker.

There are various strategies promoted when buying drives for a NAS. One is to buy all the drives in a batch so they are likely to have the same firmware versions. Another is the exact opposite - buy them from two or more places so that if there are manufacturing problems with a specific batch you won’t have problems with multiple drives. Which is better? Flip a coin. Don’t worry about having the same firmware because DSM doesn’t even care if they are the same model drive.

I buy my drives in whatever way makes sense at the time. Synology is very forgiving of mixed drive types so feel free to mix and match. If you are starting out and have some spare drives available, use them.

I’ve never specifically bought drives from different places to mix the manufacturing batches. There may be some credibility to that theory, but I view it as increasing the chances of buying into a bad batch. Plus, I’m basically lazy and find it easier to place one order.

That said, these days I’m typically buying drives one or two at a time to upgrade an existing NAS, so they are naturally spread out, both by the manufacturing batch and the warranty expiration.

Some Additional Tips

I do like to keep the drive speeds (the rotation speed such as 5500 rpm or 7200 rpm) the same within the NAS, even if they are from different manufacturers or are different sizes. While Synology doesn’t care, as long as the drives are compatible, the slowest drive will dominate the performance of the volume. So having faster drives mixed in would be a waste.

While “green” may be nothing more than a marketing term in some cases, I try to avoid green drives even if they are on the compatibility list. They may be set to power down when not being actively accessed which could affect NAS performance. I say “try to avoid” because if the price is right for a drive that is on the compatibility list for my specific Synology model then I would use them. If a green drive is not on the compatibility list I would avoid it since it’s very likely it’s not there for a specific reason.

You can determine how much usable space that you’ll have by using Synology’s capacity planner. I cover capacity planning in the next chapter.

  1. Synology has recently added the ability to use SSD drives as a cache in the NAS in order to improve performance. In this case the drive is not part of the file storage and is a separate discussion. If you plan to use an SSD cache you need to allow extra drive bays for these drives.  ↩

  2. I avoided Seagate when I had a bad run of drives from them. Then I avoided Western Digital after I had a bad run of those. Hitachi and Samsung both served me well but are now owned by Western Digital and Seagate. So I generally look at the current prices, performance and warranty when picking a drive.  ↩