RAID and Erasure Coding are two technologies used to protect data and improve availability in storage systems, but they work in different ways.
I’ll try to explain the differences simply.
What is RAID?
RAID (Redundant Array of Independent Disks) is a technology that combines multiple hard disks to improve performances and protect against data loss in any case of one or more disk failures, which is called redundancy. You can swap disks without discontinuing the service. RAID has been around for ages. The term RAID was coined in 1987 by David Patterson, Randy Katz and Garth A. Gibson at the California University.
There are a few different RAID levels, but the most common ones are:
- RAID 1:Â data is duplicated across two disks. If one fails, the other one has an identical copy.
- RAID 5: great for storing data and parity information across at least three disks. If one disk fails, you can still get your data back using the other disks.
- RAID 6: is pretty similar to RAID 5, but it’s got this extra protection that lets two disks fail.
What is Erasure Coding?
Erasure coding is a more advanced technology than RAID, used in distributed storage systems and in the cloud. It divides data into blocks and adds ‘coding’ information that allows lost data to be reconstructed even if multiple disks or nodes fail. It’s like a more advanced RAID, but it’s got more flexibility and fault tolerance. Erasure coding is just one part of the bigger picture when it comes to modern data protection.
Comparison Table: RAID vs Erasure Coding
| Feature | RAID | Erasure Coding |
|---|---|---|
| Ease of use | Easier to set up and manage. | More complex, requires advanced administration. |
| Performance | High performance, particularly in RAID 0 and 1 configurations. | It may reduce performance due to complex encoding. |
| Storage space | High waste of space (e.g. RAID 1 uses 50% of the space). | More space-efficient, particularly in large systems. |
| Fault tolerance | Limited (RAID 5 tolerates 1 failure, RAID 6 tolerates 2). | Greater fault tolerance (can tolerate more failures). |
| Data reconstruction | Faster (for a few disks failures). | Slower, particularly with large volumes of data. |
| Flexibility | Less flexible, it is based on predefined configurations. | Very flexible, suitable for distributed and large-scale systems. |
| Cost | Less expensive, mainly in small deployments. | More expensive and complex to implement, but scalable.Summary |
RAID is a simpler technology and is often used in environments where data protection and high performance are needed, but with limited fault tolerance.
Erasure Coding is more advanced and flexible, ideal for large-scale storage systems such as distributed or cloud systems, where greater fault tolerance and efficient use of space are required.
