Which file system does unRAID use

unRAID the better alternative to FreeNAS?

When it comes to an operating system for a data server "NAS", FreeNAS is often the first choice.

This is considered very reliable and safe. But what alternatives are there to FreeNAS, apart from ready-made NAS systems from Synology or QNAP?

For my new NAS system I tried a few operating systems and ended up stuck with unRAID. Why and what does unRAID do better than FreeNAS in my opinion?

Curious? Then take a look at my experience report on the subject of unRAID.


Why not FreeNAS?

Thanks to the ZFS file system, FreeNAS offers incredibly good performance, stability and reliability. Therefore, I think that FreeNAS will certainly remain the first choice for many users when it comes to an OS for a file server.

Nevertheless, FreeNAS is not perfect, especially when it comes to things other than pure technology.

On the one hand, FreeNAS is quite hardware hungry, especially when it comes to RAM. In addition to the pure capacity, FreeNAS even prefers the again significantly expensive ECC memory for optimal operation.

Hardware compatibility is also a bit more cumbersome due to the FreeBSD basis. Cumbersome also refers to hard drive configurations; hard drives of the same size must be available for a ZFS raid. A colorful mix of hard drives lying around is therefore not possible.

The bigger weakness is certainly the user experience. The installation is very simple, but the user interface is not the most modern and sometimes a bit nested and cumbersome. You want to read out smart data from the HDDs apart from any tests? Have fun! A sensible right management for releases? Only through various user groups.

On the whole, you can certainly do everything with FreeNAS, but this requires a lot of Googling. The answers are mostly based on the motto "create this script and then execute these 30 commands".

Certainly okay for an IT professional, but for someone who is looking for an OS that works quickly and easily, it is not the optimum. This is where unRAID comes into play!


Hardware requirements

As far as the hardware requirements are concerned, unRAID is very problem-free. A 64-bit capable processor must be available as well as 1GB RAM.

This is of course the bare minimum, if you want to do more than just share data, you should have a more capable processor and more RAM in the system.

I used an Intel Pentium G4620 and 8GB RAM for this test and this was completely sufficient. Without VMs, I never saw a CPU load exceeding 20%. The RAM was also only very lightly loaded with less than 1GB.


Installation and setup

The installation of unRAID is a breeze! You download the current version from the manufacturer's website, copy it to a USB stick, boot from the USB stick and you're done!

Now you can call up the web interface from another computer by entering the IP in the web browser.

When you arrive in the web interface, you can start right away, ideally by creating a storage array.



To be honest, unRAID is also not a beauty when it comes to the user interface. Synology or QNAP NAS systems play in a completely different league here.

But even the somewhat outdated user interface is much nicer and clearer than that of FreeNAS.

unRAID is very focused on the essentials. On the start page you will find an overview of all hard drives, the temperatures, the SMART status, CPU utilization, etc.

The whole thing is presented very well visually. unRAID is designed to be easy to use. This also applies to things like rights management, which is just stupid at FreeNAS.

With unRAID you can simply create users and select for each shared folder to what extent this access should exist. unRAID supports the common protocols such as NFS, SMB and AFP.


This was it in the basic functions as far as file sharing is concerned. However, unRAID can be expanded very well! On the one hand, it supports Docker containers, and on the other hand, there is the possibility of installing plugins.

The latter is extremely easy here, the unRAID community has written an app store plugin, which is simply installed by copy-paste. Other plugins, for example for reading out the CPU temperature, fan control, NTFS file system, etc. can now be downloaded and installed with one click.

With these plugins and Docker containers, all imaginable things can now be installed, such as a Teamspeak server, bit torent client, etc.

The popular PLEX server can also be used from home.

The bottom line is that this is the biggest difference between FreeNAS and unRAID. FreeNAS can do pretty much everything, but there is also a lot of googling and xyz commands in the terminal. unRAID is easier here, you can also access the terminal, but I didn't have to do this once!

Last but not least, unRAID has an ace up its sleeve, virtual machines! unRAID also supports the switching through of a graphics card without a major loss of performance. For example, you could have a Steam in Home Streaming Server running on your NAS or a normal Windows that does not have the typical VM restrictions. So you could use your gaming computer as a NAS and as a gaming computer at the same time.

This reveals various interesting possibilities of how you can use your server in other ways.


Storage configuration and RAID

In principle, unRAID initially supports up to 24 HDDs and six parity HDDs. In addition, up to six cache drives can be added.

In contrast to FreeNAS, unRAID is quite flexible when it comes to drives. You can mix and match when it comes to hard drives. These are used very efficiently, for example if you have two 8TB and one 4TB HDD and if you use a "RAID 5", 12TB storage can be used.

If you read this, I'll just assume that you already roughly know what a "RAID" is. A RAID is a combination of several hard disks or SSDs which should ensure more speed or file security. For us, in this case, RAID 5 and RAID 6 are the most interesting.

A RAID 5 consists of at least three drives, but can be expanded as required. If you now have three hard drives in RAID 5, one of the hard drives can fail, regardless of which one, without losing any files. In return, however, you also give up part of your maximum capacity. However, this is a price that you are usually willing to pay.

unRAID uses its own algorithm which is not comparable to RAID 5/6 or ZFS, but leads to a similar result.

For example, if you have five HDDs and one parity HDD in your system, any HDD can fail without losing any data. The parity HDD must have the size of the largest single HDD in the system.

unRAID does not divide data, but each file is on an HDD. This has a very obvious advantage, not all HDDs have to "start up" if you only call up one file from the server.

In addition, if the restoration of the data with the help of parity fails in the event of a hard drive failure (for whatever reason that should happen), not all data is gone.

So how does unRAID do that? Data on hard drives and SSDs consist of ones and zeros, unRaid counts these.

If you have three hard disks on each of these hard disks there is a 0 in the first sector, then unRaid also notes a 0 on its parity HDD. If there is a 0 in the second sector for two hard disks and a 1 in the third, unRAID notes a 1. Located in the third sector with two hard disks a 1 and with the third a 0 so unRAID notes a 0.

This means that the number of 1's is a 0 and otherwise a 1. If a hard drive fails, unRAID can count again and thus calculate the missing data.

For example, in the example above, HDD three fails, we would have a 0 twice in sector one and also a 0 on the parity, so unRAID knows there must also have been a 0 on the missing HDD.

Sector two, we have the 0 twice and a 1 on the parity, means it must have been a 1 on hard disk three.

The whole thing can of course be played through with any number of hard drives.

With this type of parity calculation, different memory sizes can of course be mixed well.

But the whole thing also has disadvantages, especially in terms of performance. I will go into that later.

Of course, data security is also somewhat weaker than, for example, with FreeNAS with the ZFS file system. The type of parity calculation used here protects well against a total failure of a hard drive but less against file corruption due to a defective controller, for example.

For the latter, however, unRAID can use the Btrfs file system on the data hard disks, which has good error detection (the data hard disks can use any file system and since data is not split, it can also be easily read out on other computers, only the parity Hard disks use their own file system).

The bottom line is that file security is still good with unRaid, probably better than with a hardware RAID controller, but worse than with FreeNAS. On the other hand, the hard drive arrangement and capacities are more flexible here.



The biggest weakness of unRAID is certainly its performance. I don't mean high hardware requirements, but the pure transfer rates.

I used the following hardware:

  • Intel Pentium G4620, 2x 3.70GHz, boxed
  • MSI C236M
  • Crucial 8GB, DDR4-2400, CL17, ECC (CT8G4WFS824A)
  • 4x Seagate IronWolf NAS HDD 8TB
  • Intel 10Gbit NIC

Due to the 10Gbit LAN card, the theoretical maximum transfer rate is around 1200MB / s. The HDDs manage a transfer rate of around 200MB / s.

What does unRAID create in a system with simple data security (1x parity 3x data)?

Reading the data rate was around 80-120MB / s (via 10Gbit NIC) and writing was a bit sad 40-50MB / s. The latter is of course due to the way unRAID calculates the parity.

Incidentally, FreeNAS on the same system with ZFS1 manages 450MB / s for writing and 600MB / s for reading.

Many readers will now wonder why the hell you should choose unRAID with such values. However, unRAID still has an ace up its sleeve, in order to play this ace, you need an SSD.

unRAID can use one or two SSDs as cache, so data first end up on the SSD and are slowly written away in the background.

As long as the data is on the SSD, it will also be loaded from the SSD when it is called up again. You can effectively achieve around 450MB / s writing and reading when using a SATA SSD!

Only when you write more data at once than the SSD can hold or when you call up old data does the speed drop to 40MB / s for writing or 120MB / s for reading!

For example, if you should use a 480GB SSD, I think that it is very rare in everyday life that you actually write 480GB in one go on your NAS and when reading, the performance is at the usual Gbit LAN limit anyway.

If you do not use an SSD cache, unRAID uses the RAM as usual as between storage.

Data from the SSD cache is transferred to the HDD array at night (or at a freely adjustable time). Alternatively, you can also set folders which should only be located on the SSD cache for better performance.



unRAID is the best NAS operating system (apart from the ready-made NAS systems) that I have come across so far, if you want easy and uncomplicated use!

Similar to Apple, the motto “it simply works” applies here, you don't have to mess with the terminal or anything like that. There is a simple and clear UI for everything. Should you ever need help or a feature is missing, the community will be of great help, whether via the App Store or simply with advice.

The whole thing is much less technical here than with FreeNAS and it was once friendlier. Another advantage of unRAID are the virtual machines and the hard disk configuration.

You can mix colorful hard drives here and still enjoy data protection. In addition, unRAID does not have any major hardware requirements. Do you have an old computer in the corner and a few hard drives that have been left over? That's enough for unRAID!

If you have a high-end NAS with a graphics card, you could even use the system for Steam in home streaming.

But of course unRAID is not perfect. There are two points that primarily bother me. That would be the performance and the price. Due to the way in which the parity is calculated here, unRAID is comparatively slow for write accesses. An SSD can help as a write cache, but of course only to a limited extent. I wouldn't say that this is the knockout criterion, especially if you use Gbit LAN and are limited to 120MB / s anyway, but FreeNAS would deliver significantly more performance even without an SSD cache.

The second point is the price. unRAID is not free! You have to invest between € 60 and € 120 here, which is okay, but certainly daunting. There is a 30 day trial version that you can try out.

I would also advise you to try unRAID if you are looking for a new operating system for your NAS / home server!

unRAID is not perfect and certainly not better than FreeNAS for every user, but it is definitely worth a look, especially if you want to mix hard drives.