RAID 5 vs RAID 6: It’s All About Data Protection

When you purchase several physical hard drive disks and combine them into one virtual storage device, you get a RAID array better known as a redundant array of independent disks. This is a storage method that allows you to store your information on multiple drives, boosting their read/write capabilities and decreasing the potential for data loss. If you are new to RAID Levels, we have an in-depth overview article on RAID Levels. Once you understand the basics, read this article for a detailed comparison of RAID 5 vs RAID 6.

If you are interested in other RAID level comparisons, we cover the following pairs that are most often compared:

• RAID 0 vs RAID 1
• RAID 1 vs RAID 5
• RAID 5 vs RAID 10
• Hardware RAID vs Software RAID

What Is RAID 5: Fault Tolerance Through Parity

RAID 5 makes use of a minimum of 3 disks and a combination of disk striping and parity information in order to increase both read speed and security. It starts by separating data into equal parts, and spreading those parts sequentially across all disks in the array. Afterwards, data is collected, called parity data, and placed into a formula for the system to calculate what’s missing if a disk is lost. This parity data is also separated and spread across each disk in the array, making it safe for any one disk to fail without compromising the others.

Example

Let’s say you’ve created a RAID 5 array using four disks, and have filled all of your available storage space with files named “A”, “B”, “C” and “D”. If the files are each split into three equal parts, you’d see something similar to the figure below:

Disk 1	Disk 2	Disk 3	Disk 4
File A1	File A2	File A3	Parity A
File B1	File B2	Parity B	File B3
File C1	Parity C	File C2	File C3
Parity D	File D1	File D2	File D3

As you can see, all data has been spread evenly throughout the array, meaning more can be accessed at once while being more protected by the distributed parity data.

Advantages of RAID 5

• It has quite a high read speed.
• It has data redundancy.
• It offers a stable and reliable setup.
• Rebuilding a failed drive is completed relatively quickly.
• It makes use of storage space efficiently.
• Drives can be hot-swapped to prevent downtime.

Disadvantages of RAID 5

• If two hard disk drives fail simultaneously, the entire setup fails & data is lost.
• The write speed is relatively slow due to the parity drive.
• Data restoration can take a long time.
• It can be a bit complex to set up.

What Is RAID 6: Double the Parity, Double the Fault Tolerance

This RAID level is very similar to RAID 5 in that they both use disk striping and parity data to store and secure information. However, RAID 6 stands apart by requiring an additional disk in order to add a second level of parity data that uses much more complex calculations than the first. What this accomplishes is that it allows the RAID programming to suffer the loss of two disks without compromising the others. Needless to say, this array is more expensive to implement, but offers much higher data security in return.

Example

Using the same scenario as above, we can add in the second level of parity data to produce a similar figure:

Disk 1	Disk 2	Disk 3	Disk 4
File A1	File A2	Parity A1	Parity A2
File B1	Parity B1	Parity B2	File B2
Parity C1	Parity C2	File C1	File C2
Parity D2	File D1	File D2	Parity D1

What becomes immediately obvious is that RAID 6 has a little less available storage than RAID 5. However, the second level of parity data spread out in this configuration means there should nearly always be enough data to reconstruct any lost information. If, for example, both Disk 2 and 3 fail at the same time, both D files will be lost, but are easily rebuilt as both Parity D files remain untouched.

Advantages of RAID 6

• It comes with a high fault tolerance and data redundancy.
• It has reasonably fast read operations.
• Data accessibility is excellent.
• It supports up to two disk failures.
• It is highly secure due to double parity.

Disadvantages of RAID 6

• The write speed is very slow due to double parity.
• It is complex to set up.
• If three or more disks fail simultaneously, all data is lost.
• Restoration takes a long time.

RAID 5 vs RAID 6 Comparison Chart

	RAID 5	RAID 6
Basic Function/Key Feature	Disk Striping With Parity Check System	Disk Striping With Double Parity Check System
Storage Disks Required	3 or More	4
Storage Capacity	60-75% or 1 Drive Worth of Space is Lost	Similar
Parity Check System	Yes – Parity – Single Disk	Yes – Parity – Double Disk
Fault Tolerance	Yes – 1 Drive Can Fail	Yes – 2 Drives Can Fail
Data Recovery	Yes – Using the Parity Check System	Yes – Using the Parity Check System
Overall Cost	Expensive	More Expensive
Disk Read Performance	Fairly Quick	Reasonably Fast.
Disk Write Performance	Slow	Slower
Write Penalty?	Yes – Slightly Due to Writing to the Parity Block	Yes – Heavy Due to Writing 2 Parity Blocks
Appropriate Purpose	A Balance Between Speed & Data Security	A Greater Focus on Data Security

*Note: storage capacity differs based on how many drives you are using in your RAID configuration.

RAID 5 vs RAID 6 Critical Distinctions

• RAID 5 uses single parity striping while RAID 6 uses double parity striping.
• RAID 5 is a bit cheaper to set up because it requires 3 minimum disks, while RAID 6 needs a minimum of 4.
• RAID 5 has better storage capacity at 80% while RAID 6 provides 60%.
• RAID 5 can support a 1-drive failure, while RAID 6 can support a 2-drive failure.
• The read performance between RAID 5 & 6 are similar, while RAID 6 has a slower write performance due to the additional parity disk.
• To create a RAID 5 array, you can use a RAID software controller, while RAID 6 array must use hardware.

Use Cases: When to Use RAID 5 in Real Life Scenarios

With RAID 5, you get an excellent balance between storage capacity, performance, and some fault-tolerance with only the use of 3 hard disk drives. This makes RAID 5 good for the following scenarios:

• You are on a shoestring budget and need fault-tolerance protection without sacrificing performance or storage space.
  
• You are running an application or file server that needs data to be quickly accessible, good performance, and lots of storage space. RAID 5 works well for dedicated servers for large news websites or email servers for large corporations.
  
• If you do not care about the extra fault-tolerance that RAID 6 brings, and you need quicker data recovery, RAID 5 works better. If you are in a situation where you don’t have the money for a hardware RAID controller or you need efficient storage space, RAID 5 is better.
  
• Better for small to medium-size businesses that have servers that are limited to 3-16 hard drives.

Use Cases: When to Use RAID 6 in Real Life Scenarios

With RAID 6, you get greater data protection due to the higher fault-tolerance, which makes this RAID level really good for high-availability applications such as:

• Online customer service portals or standard web servers where the need for read performance outweighs write transactions.
  
• Servers where archiving and backups are needed due to high capacity of data. This reduces the change for data loss due to the double parity system.
  
• In situations where losing critical data cannot happen but you don’t need to rely on fast write speeds.
  
• Better as an all-around data storage system for servers that have larger data storage drives; useful on enterprise levels.

Frequently Asked Questions

Wrapping It Up

Despite the similarities between RAID 5 and 6, each level offers different magnitudes of speed and protection. While RAID 5 focuses on providing a balance between the two, RAID 6 sacrifices some extra write speed and storage in order to ensure as much data security as possible.