NAS server

Synology 2019 Buying guide Part 2: How much storage do I need?

Are you looking for a Synology NAS but you find all the models confusing? How big should your disks be? RAID or not RAID? Many questions, many decisions before you know what you need to buy.

I am in the process of buying my third synology, so I decided to document the process, so you can follow my journey and hopefully it will help you decide!

In this upcoming series, I want to guide you through the buying process and the installation of a Synology NAS.

  1. Part 1: Explaining Synology NAS models
  2. Part 2: Storage needs (this post)
  3. Part 3: Which synology should I buy then?

In this blog post I will explain the different storage types available and how you can estimate how much storage you need based on that.

Lets get started!!!

How much storage do I need for my Synology NAS?

Now that you know what models are available to you, you need to decide how much storage capacity you need.

There are two things you need to consider when you estimate how much storage you need:

  1. This is an obvious one, but needs to be said: How much data do you want to store? Make sure you think ahead so you have a possibility to grow.

Check how much data you have today and multiply that by 3 or 4, so you can use your NAS for at least 3-5  years. I have outgrown my 2x3TB in just 6 years.

2. Next is which storage type you intend to use.

When it comes to storage types,we need to look at which types Synology supports.

Synology Storage

Synology NASes support 2 types of storage systems: RAID and proprietary system SHR.

We will go through the difference between RAID and SHR when we configure our NAS, it is not important now, but what you need to know is what each raid type is so you can determine how many disks and capacity you need to buy.

What is RAID and why do you need it?

RAID stands for Redundant Array of Independent Disks.

And what is RAID used for? Well, a RAID system uses two or more hard drives to improve performance and provide fault tolerance, meaning, if a drive fails, the server still can operate and decreases the chances on data loss on that machine.

RAID is not a full proof backup system, you still need additional back up method, but let me talk about the types of RAIDs available first before I explain why this is true.

Types of RAID

Synology has a fabulous guide that shows us what those technologies are and how many disks you need to get one or the other.

But lets go through them quickly:

Raid 0:

You need two disks, and data gets divided and stored in the different disks. This is very fast but if one drive fails, you lose all data.

raid 0 synology nas

So why does Raid 0 exists? Well, as data is written across multiple disks, it increases the performance of the server, but again, if one disk fails, you lose it all.

One advantage of RAID 0 is that you can use most of the capacity of both disks, so if you buy 2x10TB of capacity, you can use both disks.

raid 0 storage utilization

No RAID system is a back up solution, but for sure RAID 0 is not. If you don’t have another back up for your data, stay away of RAID 0.

Moving on….

Raid 1 or SHR:

Raid 1 requires two disks, and the same file is copied in both disks, so if a disk fails, the information can be recovered from the other disk.

raid 1 synology nas

What are the cons on this?

  1. Performance penalty as data needs to be copied twice and
  2.  if you buy 2x2TB disks, you can only use 2TB.

raid 1 storage utilization

Is RAID 1 a back up solution?

Think about this scenarios:

  • You accidentally delete a file –> It gets deleted on both disks
  • Your disk is corrupted by a virus –> the corruption extends to both disks
  • Your house get hits buy a thunder –> both disks get fried…

….you get the point right?

Back up and redundancy is two different things. RAID is not a backup solution.

A RAID solution is meant to protect you against hardware failure, but when it comes to the protections of the data or files, you need to look else where, like external backups, snapshots, hyper backups etc…


So, what is the deal with RAID 5? Well, it brings the best of both worlds, (meaning RAID 0 AND 1) , it splits the data into 2 disks and then has one for security in case one disk fails. In other words, RAID 5 provides better performance than RAID 1 but has fault tolerance (lacking in RAID 0) meaning if one drive crashes, you can still recover your data. (… kind of… check RAID6 to know why).

raid 5 synology nas

Also if one disk fails, it can be replaced without shutting down your NAS, which is a big plus for enterprise use.

If you buy 3x10TB disks, then you will be able to use 2 and the third will be used for recovery purposes.

raid 5 storage utilization


And then there is a RAID 6 and why do we need another RAID type when we already have the best of both worlds, you might wonder..

Well, here is another “but” with RAID 5, and this is specially true with larger disks. If one of your disks fails, it is possible for the recovery disk to fail as well. Crazy right? And that is where RAID 6 comes into play: it requires minimum of 4 disks. Data is divided across 2 disks and the remaining 2 are used for recovery, so in a RAID 6 you can have 2 disks fail and still have a chance to recover your data.

Phew!! ….

raid 6 synology nas

The penalty of RAID 6 is that you lose two drives when you buy four.

raid 6 storage utilization

And then there are combinations of those RAID types.

How much storage do I need?

Ok, so to the point now, how much storage do you need? If you remember what I said in the beginning, your storage needs will depend on:

  1. How much data you want to store in your NAS
  2. The level of “protection” you want to achieve

Now, let me give you a concrete example: my needs for a new NAS, so you can follow my thinking:

Even though I own two other NASes, I run a youtube channel and I produce a lot of content, both with normal cameras, but also with drones, and gopros. Those files takes an incredible amount of space (I save a copy of my work) and my disks are full. The files are “Backed up by google/youtube”, but it is a pain to have to download something I already created, so I want to have my own copy.

Also, I am backing today those files to my NAS in Spain, which is insane! Those files are huge and it is clogging my and my dad’s network, so I need more space and to stop moving those files across the internet.

Today I have 3TB of content (crazy right? That is what 3 years of youtubing will do to you!) and I need space to grow for at least the next 5 years, so I want to have 20TB of data storage.

Now, all the data is available online, I just want to have a quick access to my files, but if a disk fails, I prefer to be able to restore it that to have to download anything again, so I am going for RAID 6, that means that I need 4 disks.

So, I need 20TB for RAID 6 which means I need 40TB(!) of storage.

Now, do your math, how much data do you need? Once we have done that, it is time to pick a NAS to buy.

I will show you in my next post which one I bought and why.


7 thoughts on “Synology 2019 Buying guide Part 2: How much storage do I need?

      1. It’s will be going in a ds1019+ hopefully arriving next week, I also bought 2 m2 ssd drives for the cache, which will get installed in the bottom


  1. You have me wondering what is the correct way to format them to not get the worst of both parts?

    I could add a second 1tb ssd, if that would make formatting easier.


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