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:

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 1Disk 2Disk 3Disk 4
File A1File A2File A3Parity A
File B1File B2Parity BFile B3
File C1Parity CFile C2File C3
Parity DFile D1File D2File 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.
RAID 5 disk array

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 1Disk 2Disk 3Disk 4
File A1File A2Parity A1Parity A2
File B1Parity B1Parity B2File B2
Parity C1Parity C2File C1File C2
Parity D2File D1File D2Parity 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.
RAID 6 disk array

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 5RAID 6
Basic Function/Key FeatureDisk Striping With Parity Check SystemDisk Striping With Double Parity Check System
Storage Disks Required3 or More4
Storage Capacity60-75% or 1 Drive Worth of Space is LostSimilar
Parity Check SystemYes – Parity – Single DiskYes – Parity – Double Disk
Fault ToleranceYes – 1 Drive Can FailYes – 2 Drives Can Fail
Data RecoveryYes – Using the Parity Check SystemYes – Using the Parity Check System
Overall CostExpensiveMore Expensive
Disk Read PerformanceFairly QuickReasonably Fast.
Disk Write PerformanceSlowSlower
Write Penalty?Yes – Slightly Due to Writing to the Parity BlockYes – Heavy Due to Writing 2 Parity Blocks
Appropriate PurposeA Balance Between Speed & Data SecurityA 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 news 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

Is RAID 5 or RAID 6 Faster?

Both RAID levels offer comparable read speeds, however, RAID 5 offers a higher write speed than that of RAID 6, due to RAID 6 having an additional level of parity to compute and assemble.

Is RAID 5 or RAID 6 Safer?

The extra level of parity data implemented by RAID 6 boasts much higher data security, as it can tolerate two drives failing for any reason and still be able to recover any lost data.

Which is Better, RAID 5 or 6?

That entirely depends on what’s more important to you; speed, or security. RAID 5 has marginally better write speeds and storage space, while RAID 6 has much better data security.

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.

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