12/27/2011- The latest NAS from Thecus, the N4100EVO, features a very fancy dual-core Cavium CPU designed to provide a very good value in term of price and energy consumption without cutting performance. However, disks capacity is rising as never before and people start considering 3TB as an option while the industry is developing 4TB and more. On a 4 bay NAS with 3TB HDD, a total of 12TB raw data capacity, even the most robust CPU can have a hard time dealing with all that data in a RAID environment. Why is that so? And how can this problem be solved? Let's find out the answers together.
RAID 5 and RAID 6: A lot of computations for your protection
Before understanding how an XOR engine can be useful, it's important to know how RAID volumes work. For RAID 0 and RAID 1 it's really easy: data is just copied or split. But for RAID 5 and RAID 6, the most widely used RAID levels on 4 bay NAS, it's slightly more complicated (1).
Data is made up of bits. To simplify, bits are the simplest and tiniest elements in the computer world: it's either 0 or 1 and everything can be transformed into a (long) series of bits. For example, the word “Hello” translated into binary (the language using bits) is “0100100001100101011011000110110001101111” (2). Sometimes the simplest things can look a bit complicated! But why are people using bits in this case? Because it allows a lot of specific and powerful operations named logical operations which can be handled by electronics components (3).
One of those operations is XOR (pronounced eks-or or zor), a calculation widely used in RAID 5 and RAID 6 to create RAID volumes and protect our data in case of disk(s) failure. The problem is you need a tremendous amount of XOR operations! Our word “Hello” on a 3-disk RAID 5 volume would require at least 10 XOR operations just to be written (4). Now you can imagine why writing terabytes of data to a RAID partition can be hard for CPUs: billions of XOR calculations are needed. And that's even worst when rebuilding RAID in the case of a disk failure: your data is not protected anymore.
XOR Engine: Taking a load off the CPU
To speed up these processes, Thecus decided to integrate what is called an XOR engine inside the N4100EVO. In a nutshell, it's a small piece of hardware entirely devoted to XOR calculations that shares the workload with the main CPU, a bit like a dedicated assistant.
With the CPU's load lessened, it can then be put to good use for the user: sharing data, streaming media, connecting with mobile devices, along with the whole range of the N4100EVO's functions. On a similar NAS without an XOR engine, transfer rates can drop by almost 50% during RAID building and rebuilding, compared to the N4100EVO will only slow down 15-20%. RAID 5 building and rebuilding are also 20% faster, decreasing the time your NAS is vulnerable and increasing data protection (5)!
Your NAS will execute its tasks faster and will live longer because the workload will be more balanced among its components!
If you want to know more about RAID levels, the Wikipedia article is an excellent reference:
You can have fun here converting sentences into secret messages!
For people strongly interested into logical operations, welcome to the Electronics Club :
A simple and very interesting explanation about RAID 5:
Tested on an N4100EVO and an N4100EVO populated with 3xHDD (500GB, 7200RPM): 4GB file transfer through SAMBA.
Learn more about the N4100EVO here:
Established in 2004, Thecus Technology Corp provides market leading network attached storage and network video recorder solutions, committed to revolutionize how everyone from home user to enterprise level business centrally stores, manages and accesses their digital data both onsite and cloud-based. Thecus strives to deliver continuous innovation through cutting edge technology and design to provide data storage with the most customer-friendly platform, rapid performance and robust security. In May 2016, Thecus was formally acquired by Ennoconn Corporation and thus became part of the Foxconn IPC Technology group. Partnered together this diverse group of companies work in tandem to provide a total IoT (Internet of Things) solution. Now with an unparalleled portfolio to work with, Thecus is collaborating to bring unprecedented change to the network storage industry.