When setting up a RAID (Redundant Array of Independent Disks) system, one of the most important choices is which RAID level to use. The RAID level determines how data is distributed across the disks in the array and what level of redundancy and performance the system provides.
There are several common RAID levels to choose from, each with its own advantages and disadvantages. There is no single “best” RAID level – the right choice depends on your priorities for capacity, performance, redundancy and cost. In this article, we’ll go through the most popular RAID levels and when each one is the best choice.
What is RAID?
RAID is a technology used to create storage systems out of multiple physical disk drives. The main goals of RAID are to provide increased storage capacity, redundancy to protect against drive failures, and improved performance compared to a single drive.
A RAID system combines physical drives into logical units called RAID arrays. Depending on the RAID level, data can be duplicated across multiple drives (known as mirroring or parity), providing fault tolerance in case a drive fails. The RAID controller handles distributing/duplicating data across the array.
Some key terms:
- RAID 0: Striping without parity or mirroring. High performance but no redundancy.
- RAID 1: Mirroring. Two identical copies of data. Provides redundancy.
- RAID 5: Striping with distributed parity. Good performance plus redundancy.
- RAID 6: Striping with double distributed parity. Excellent redundancy but reduced write performance.
- RAID 10: Striping and mirroring. High performance and excellent redundancy.
What are the most popular RAID levels?
The most commonly used RAID levels are:
- RAID 0 – Data is striped across multiple drives. Provides high performance but no redundancy.
- RAID 1 – Drives are mirrored. Provides redundancy but lower capacity.
- RAID 5 – Data is striped across drives with distributed parity. Good performance and redundancy.
- RAID 6 – Similar to RAID 5 but with double distributed parity. Excellent redundancy but slower write performance.
- RAID 10 – Striping and mirroring combined. High performance and high redundancy.
What is the best RAID level for performance?
If your main goal is maximum performance, then RAID 0 is generally the best option.
With RAID 0, data is striped evenly across multiple drives with no parity or mirroring. This allows reads and writes to be done in parallel across multiple drives for faster performance.
However, RAID 0 provides no data redundancy. If one drive fails, all data will be lost. As such, RAID 0 is generally used when performance is critical but data redundancy is less important.
Other high performance RAID options
- RAID 10 can match or exceed RAID 0 performance in many cases while also providing redundancy through mirroring.
- RAID 5 can provide good performance when using high capacity SATA or SAS drives. Write performance is slower than RAID 0 or 10 due to parity calculation overhead.
What is the best RAID level for redundancy?
If your priority is protecting your data through redundancy, then RAID 6 is generally the best option.
RAID 6 provides double distributed parity, meaning data can survive up to two drive failures without losing access to data. This makes it the most redundant option.
However, RAID 6 writes require more parity calculations, so write performance will be slower than RAID 0 or 10. But reads can still be fast.
Other redundant RAID options
- RAID 10 also provides excellent redundancy through mirroring, though “only” single drive failure tolerance per mirrored set.
- RAID 5 provides single drive failure redundancy through distributed parity.
What is the best RAID level for capacity?
If you want maximize storage capacity, then RAID 0 or RAID 5 are good options.
With RAID 0, the total capacity is the sum of all the drives. But there is no redundancy.
RAID 5 capacity is the total of all drives minus one drive for the parity information. It provides redundancy unlike RAID 0.
Other high capacity options
- RAID 6 total capacity is the total of all drives minus two drives for double parity.
- RAID 10 offers mirroring so requires at least two drives per “set”, reducing overall capacity.
What is the best RAID level for cost effectiveness?
If your goal is to optimize for best cost per gigabyte of storage, then RAID 5 often provides the most cost effective option.
Compared to other redundant RAID levels like RAID 6 or RAID 10, you can get significantly more usable capacity relative to the number of drives with RAID 5.
The performance of RAID 5 is also decent, though not as fast as RAID 0/10 for writes or reads. Overall it provides a good balance of capacity, redundancy, and cost.
Other cost effective options
- RAID 1 can also be cost effective if you only need two drives total for redundancy.
- RAID 0 maximizes capacity and performance for the lowest hardware cost, but has no redundancy.
What is the best RAID level for home or small business NAS storage?
For home and small business NAS (network attached storage) devices, RAID 1 or RAID 5 are generally good options that provide a balance of performance, capacity and redundancy.
For home users, RAID 1 provides an easy setup with only two drives and protection against drive failure. But usable capacity is limited to a single drive.
For additional capacity with redundancy, RAID 5 is a good choice for small/home office NAS devices. Usable capacity is the total minus one drive, and it provides single drive fault tolerance.
Other NAS RAID options
- RAID 0 maximizes capacity and performance but has no redundancy.
- RAID 10 provides excellent redundancy and speed but requires at least 4 drives.
What is the best RAID level for enterprise/data centers?
For enterprise and data center environments where performance, capacity and redundancy are critical, RAID 10 or RAID 6 are generally the best RAID level options.
RAID 10 combines mirroring and striping to provide high speed, good capacity relative to number of drives, and high redundancy. It’s the preferred RAID level for applications requiring high performance and maximum uptime.
For secondary storage that doesn’t need as much performance but still requires excellent redundancy, RAID 6 offers double parity making it highly tolerant to drive failures. Capacity is still decent relative to number of drives.
Other enterprise RAID options
- RAID 5 can be used for some secondary applications where performance requirements are lower but redundancy is still needed.
- RAID 0 maximizes capacity and performance but lacks redundancy, making it unsuitable for most critical systems.
Quick Pros and Cons of Main RAID Levels
| RAID Level | Pros | Cons |
|---|---|---|
| RAID 0 | High performance, maximizes capacity | No redundancy |
| RAID 1 | Simple mirroring, easy to implement | Higher cost, lower capacity |
| RAID 5 | Good performance, capacity and redundancy balance | Slower writes than RAID 0/10 |
| RAID 6 | Excellent redundancy | Slowest writes, reduced capacity |
| RAID 10 | High performance, good redundancy | Higher hardware requirements |
How do I choose the right RAID level?
Here are some tips for selecting the best RAID level for your needs:
- Consider your priorities – capacity, speed, redundancy, cost? Balance these based on your needs.
- Lower capacity requirements allow more options, like RAID 10 or RAID 6.
- If uptime and data protection are critical, lean towards more redundant options like RAID 6 or 10.
- When in doubt, RAID 5 or RAID 10 provide a good blend for most general purpose uses if redundancy is needed.
- Calculate your true usable capacity and required number of drives for any option you are considering.
- Think about future needs – more capacity or drives? Higher redundancy requirements?
There is no universally best RAID level. The right option depends on your priorities for performance, redundancy, usable capacity and cost. Consider the pros and cons of each option against your needs.
Conclusion
RAID provides a way to create large storage arrays out of multiple drives and offers options to balance performance, redundancy and capacity. There is no single best RAID level for all situations – the right choice comes down to your specific needs and priorities.
RAID 0 maximizes capacity and speed but lacks redundancy. RAID 10 provides excellent performance and redundancy. RAID 5 balances capacity, speed and redundancy for general use. And RAID 6 offers the maximum redundancy. Take the time to determine your priorities and match them to the RAID level that makes the most sense.
Using the right RAID level allows you to get optimal storage performance, protection and capacity characteristics for your environment and applications.
