1.2 Requirement Gathering

Posted by JTSF at Friday, May 10, 2013 Read our previous post

Before we fill our shopping list, let's sit down and consider wisely; what features and requirements do we need in our custom made NAS?

Cost
I rank costing as the top factor over the others. If the cost of your custom-made NAS exceeds off-shelve solutions, what's the point of building it? Use the methodology below to compute a budget:

First, identify how many HDDs is your NAS gonna house. (Be realistic)
Next, check out the prices of those off-shelve NAS which has the same number of HDDs you have in mind.

For this project build, I wanted a 4 - 6 bay NAS. At the point of writing, a Synology DiskStation DS413j is selling for SGD$489. Hence, my budget for this project will be capped at $450. 


Resiliency
In systems design, this is one of the most talk about feature. For NAS, I will  construct a system that is resilient to hardware faults and software corruption.

Golden question: How to make your system resilient?

Option 1. Double every component
Wait...this is not feasible. Do you see any desktop that has dual motherboard or cold standby power supply?

Option 2. Use all hardware components that is dispensable
This is certainly achievable. For hardware components, I shall use parts that can be easily acquired locally. If the motherboard goes bonkers one of these days, I just need to make a trip to SLS (IT Mall). By getting another similar motherboard (it can be different make / model), I will be able to easily replace it and minimize the downtime. Alternatively, like how Elva (my gang) suggested, why buy hardware maintenance from a vendor? Buy two of everything! IF the NAS you are gonna build is so damn critical AND you have spare cash, buy 2 of every component!

Off-shelve NAS puts me off with their customized components. The pictures below show the internal view of Synology DS413j (left) & DS413 (right). You can estimate the downtime if you face a hardware issue. Count yourself fortunate if they have ready parts or else expect more delay when there's a need to ship in / out.

The pictures are sourced from here:
Synology Diskstation DS413j Review & Unboxin
XBit Reviews Synology DS413

The topic of resiliency covers a wide range of subjects. I will go in depth to touch on features like RAID, Dual Network Connectivity, Operating System in later part of this blog.

Energy Saving
NAS are meant to be operational 24x7. If your build is a power hungry appliance, you will see your electricity bills going up with SP Services (the power company) smiling at you. Besides, it does not do Mother Nature any good. Intel & AMD dominate the consumer market today and my selection of processor will be between these two giants. As such, we will base on an off-shelve NAS with Intel processor as a reference. The Synology DS412+ comes with dual core Intel Atom D2700 running at 2.13GHz. On the product page, it's power consumption is recorded as: Power Consumption : 44W (Access); 15W (HDD Hibernation). You can also check the specifications here: Synology DS412+ Specifications & Synology CPU Wiki

In my build, I will select power efficient components and pay close attention to the power consumption in order to meet this stringent requirement.


Scalability
This is an optional feature and it is very subjective. Some want it some don't. Ask yourself:

1. Do you plan on adding more HDDs to the enclosure? (note: the key word is adding and not replacing)
2. Do you need your HDDs to be Hot swappable?

If your answer is yes, get an enclosure that best suits your requirement. But mind you, it is very challenging to get an ideal NAS enclosure in Singapore.


Operating System
There are a variety of OS out there for NAS -  FreeNAS, NAS4Free, unRAID, CryptoNAS, NASLite, Openfiler, OpenMediaVault, EasyNAS, SnapRAID. Some are open source while others you need to pay. I doubt any consumer would be able to test each one out so I will be looking for these OS features:

1. Ease of installation and user experience (GUI pls!)
2. Offers a RAID system that is resilient and scalable.
3. Preferably, FOC.
4. Materials and resources are openly accessible.
5. Widely adopted by the public which also means more support and communications in forums.


Applications 
Quote:
Ah Kim (my gang) always says, "What about the apps? If the NAS don't have apps, it's a file server!"

This is an important feature that won majority of the consumers to buy a Synology. Honestly, Synology has done a great job in integrating their products with numerous apps. I doubt any NAS OS out there is able to compete with them at this moment. But hey! what if I am able to install Synology OS to enjoy the apps?

Multi-Functions
The idea of using my NAS as a HTPC struck me when I came across ASUSTOR. If you are not aware, ASUSTOR is a subsidiary of ASUS. After reading ASUSTOR AS-604T review, I wonder would my DIY NAS be able to double as a HTPC. Despite the fact that I favor the concept, "clear segregation of roles", this is definitely not a key requirement but a bonus feature. Good to have, not a must.