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Do you want to know which is better between the RAID 5 and RAID 6 disk arrays? To find out you’re welcome to read this complete RAID 5 vs RAID 6 comparison.
Overview
A Redundant Array of Independent Disks (RAID) is a set of disks (either HDDs or SSDs) connected to form single logical drives. Such multiple disk connections help to manage disk failure while providing massive storage space to a computer.
In a RAID vs RAID 6 setup, the data you store is spread across multiple disks. Since your data is distributed this way, you can restore them when a disk fails.
To achieve this, one or more disks will be reserved for storing recovery information. This data recovery information is called “parity information”.
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Consequently, RAID 5 and RAID 6 are used as storage for enterprise server machines. This helps an organization recover its data in case of a disk failure (or in some cases, multiple disk failures – more on this shortly).
In particular, RAID 5 requires a minimum of three hard disks. The equivalent size of one disk will hold the parity information while the remaining space will store your data.
In RAID 6, a minimum of four disks are connected in parallel. Also, unlike RAID 5, RAID 6 stores parity information using the equivalent size of two disks.
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Also, both RAID 5 and RAID 6 can have up to 32 separate disks connected together.
One important fact is that both RAID 5 and RAID 6 are not very easy to configure or understand. So, let me explain in detail how the two RAID technologies work.
RAID 5 vs RAID 6: How They Work Compared
In a RAID 5 setup, the different data you store is striped across multiple disks. The parity information is stored equally on all the disks one per disk (see the image below).
If one disk fails in a RAID 5 setup (array), all you need to do is replace the failed disk with a new disk. Then, the parity information on the other disks is used to restore the data in the new disk.
However, if two disks fail in RAID 5, the parity information can’t be used to repair them. This implies that the entire RAID 5 array may fail and the data may be lost.
Therefore, if you have 3 hard disks each having 2 TB capacity, RAID 5 will store your data using 4 TB. That is the equivalent size of two disks.
Meanwhile, the data recovery (parity) information will occupy 2 TB. That’s because it takes the size of one whole disk to store parity.
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In RAID 6, parity information is spread twice on all the disks (double parity). This enables RAID 6 to handle the simultaneous failure of two disks (see the image below).
If two disks should fail in RAID 6, all you need to do is replace the failed disks with two new disks. Then, the double parity information on the other disks is used to rebuild the data in the new disks.
Nevertheless, the failure of two disks rarely happens.
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Therefore, if you have 4 hard disks each having 2 TB capacity, RAID 6 will store your data using 4 TB space. That is the equivalent size of two disks.
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Then, it will store the double parity using another 4 TB space. That is the equivalent size of another two disks.
In summary, this means that RAID 6 offers less storage space for data compared to RAID 5. It also means that RAID 6 offers better fault tolerance than RAID 5.
RAID 5 vs RAID 6: Features Compared
I believe the previous overview of RAID 5 vs RAID 6, and my explanation of how they work have brought you closer to understanding these RAID technologies.
In the following sub-sections, I will compare the main features of RAID 5 vs RAID 6. So, the features of the two storage technologies are as follows.
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As I already stated in this guide, you need a minimum of 3 disks to create a RAID 5 array.
On the contrary, a RAID 6 array requires a minimum of 4 disks. However, both RAID types offer differences in disk storage availability.
The storage capacity of a RAID 5 array is (N-1), multiplied by the size of the smallest disk in the array. Note that N represents the number of individual hard disks in use.
For example, for a RAID 5 array with four units of 512 GB drives, the storage capacity of the array is:
(4-1)*512 GB = 1536 GB (1.536 TB)
In a RAID 5 array, you lose one hard drive.
For a RAID 6 array, the capacity of the array is (N-2), multiplied by the size of the smallest disk.
Continuing with the previous example, a RAID 6 array with four units of 512 GB disks has its capacity as:
(4-2)*512 GB = 1024 GB (1 TB)
While you lose 1 disk in a RAID 5, for a RAID 6 you lose 2 disks.
Software vs Hardware RAID Configuration
A software RAID does not require RAID hardware but a hardware RAID does. Hardware RAID is better because it’ll allow you to configure custom RAID levels with better performance.
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In other words, you can create both software and hardware RAID 5. On the contrary, a RAID 6 array requires RAID hardware only.
Cost of Implementation
Based on the last two compared features, RAID 6 array requires one additional disk and provides half the capacity of all available disks.
RAID 6 also requires a RAID card (hardware). All these add to the cost of implementation compared to RAID 5.
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Read and Write Performance
The read performance of a RAID 5 array is very close to that of a RAID 6. However, the write performance of a RAID 6 array is slightly slower.
Specifically, the slower write speed of RAID 6 is due to the additional parity information that needs to be calculated.
This means that, if implemented with the same number and types of disks, a RAID 6 array may be marginally slower than a RAID 5 array.
Having said that, a RAID 6 array provides one major recovery benefit. That is, the ability to recover in the event of 2 simultaneous disk failures.
In most circumstances, this benefit far outweighs the marginal drop in performance due to the complexity of parity information computation.
Recovery From Failure
As I stated earlier in this guide, you can recover a RAID 5 array if 1 disk fails. But if 2 disks fail simultaneously, recovery may be impossible.
This means that you may experience a data loss.
However, a RAID 6 array can recover from 2 simultaneous disk failures. This is one benefit of using a RAID 6 instead of a RAID 5 array.
Pros of RAID 5 vs RAID 6
Both RAID Levels Deliver Reasonably Fast Read Operations
Both RAID 5 and RAID 6 achieve a high data read speed. This is due to having multiple numbers of disks.
Their multiple disks help to speed read operations up.
Moreover, the striping of data allows parallel access to several parts of a related data block. So, devices can complete a read process much faster.
RAID 5 and RAID 6 Can Rebuild After a Failed Drive Replacement
As I explained earlier, one of the purposes of the RAID setup is to manage the effect of disk failure.
When a single disk fails on RAID 5, you can replace the failed disk with a new one. The parity on the remaining disks will be used to rebuild data on the new disk.
This functionality prevents data loss in case of hard disk failure.
Likewise, when two disks fail simultaneously on a RAID 6 setup (which is quite unlikely), their data is recoverable. All you’ll do is replace the two damaged disks with new ones, and the double parity will repair them.
High redundancy. Data redundancy is the existence of data in other places in addition to the actual data.
The additional data can be a complete copy of the actual data (repetition). Also, it can be a piece of data that allows the reconstruction of lost or damaged data.
This permits the correction of errors in stored or transmitted data.
As I have highlighted earlier, in comparing RAID 5 vs RAID 6, both have such a piece of data for the reconstruction of damaged data. This piece of data is called parity information.
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Archiving and Backup
RAID 6 works well for archiving and backups and on servers with large capacities as it reduces the chances of data loss due to double disk failures.
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Both RAID 5 and RAID 6 offer a good compromise between cost and performance optimization compared to separate hard drives. So, companies use it on database servers for recording transactions.
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They Offer Slower Write Speeds Than in Other RAID Configurations
Writing (saving) data on RAID 5 is slow, and writing data on RAID 6 is even slower. Compared to other RAID configurations, both RAID 5 and RAID 6 are slower in writing data.
Data Restoration Can Take Time
RAID 5 rebuilds can take a day or longer, depending on the storage controller’s speed and workload. If another disk fails during the rebuild, then it will permanently lose the data.
RAID 6 can handle a second disk failure during a rebuild.
However, if rebuilding one failed drive can take a long time, how about rebuilding a second drive? Definitely, this will take a longer time.
Both are Complex to Implement
Building a RAID from scratch can be difficult. Rebuilding a damaged RAID is also a complex task.
Whether you are talking of RAID 5 or RAID, the implementation is time and energy-consuming. It also requires technical know-how before one can successfully set up a RAID 5 and RAID 6 computer storage.
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Three Disks Failing Simultaneously Results in Data Loss
None of the two RAID configurations discussed in this article can recover from more than two disks failing concurrently.
Precisely, RAID 5 can only tolerate one disk failure. On the other hand, RAID 6 can tolerate a maximum of two disk failures.
Nevertheless, multiple disk failure is very unlikely to happen in the RAID 5 or RAID 6 setup.
Both RAID Levels Sacrifices Storage Space in Exchange for Data Availability
Both RAID 5 and RAID 6 do not offer the whole space of the constituent disks for file storage.
In RAID 5, you lose one whole disk space for recovery information (parity). You even lose more space on RAID 6 – it sacrifices an equivalent capacity of two disks for parity.
Conclusion
This guide compared RAID 5 vs RAID 6. Both RAID implementations use striping with distributed parity.
Neither of the two RAID configurations is better or worse. Nevertheless, RAID 5 gives a little more storage space and faster rebuilds, while RAID 6 gives more data protection.
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RAID 5 uses 1 parity function and can recover from one disk failure while RAID 6 uses 2 parity functions. The effect is that you can recover a RAID 6 array with 2 simultaneous disk failures.
Therefore, RAID 6 is a better choice when it comes to data security which is paramount for enterprises. However, RAID 5 gives more storage space than RAID 6.
I hope I was able to explain RAID 5 vs RAID 6 and how they function. I also hope that you found the article easy to understand.
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Finally, you may find other helpful articles on our Storage & Disk Technology Explained page.
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