As data storage needs grow, many computer users face the question of whether to configure multiple hard disk drives (HDDs) in a RAID array. RAID (Redundant Array of Independent Disks) allows multiple disk drives to function together for increased performance, capacity, or reliability. While RAID can provide benefits, it also carries some risks and requires careful planning. This article examines the key considerations in deciding whether RAID is right for your storage needs.
What is RAID?
RAID is a technology that allows two or more physical hard disk drives to be grouped together to improve performance and/or reliability. The different configurations of RAID provide different benefits:
- RAID 0: Also called disk striping, RAID 0 splits data evenly across two or more drives. This improves performance by allowing reads and writes to be distributed across multiple disks. However, it provides no redundancy – if one drive fails, all data will be lost.
- RAID 1: Also known as disk mirroring, RAID 1 duplicates all data across two or more drives. This provides full redundancy, as data remains accessible if one drive fails. But total capacity is limited to the size of the smallest member drive.
- RAID 5: RAID 5 stripes data and parity information across three or more drives. If one drive fails, the missing data can be recalculated from the parity information. RAID 5 provides redundancy while also allowing for larger capacity.
- RAID 6: Similar to RAID 5, but with double distributed parity information to allow for two drive failures.
- RAID 10: RAID 10 mirrors two drives, then stripes these sets in a RAID 0 configuration. Provides redundancy and improved performance.
There are additional RAID configurations, but these are among the most common. Key factors in choosing a RAID level are the priorities for performance, capacity, and fault tolerance.
Benefits of RAID
There are several potential benefits that a RAID array can provide:
- Increased storage capacity – Combining multiple drives adds their capacities together in many RAID configurations.
- Improved performance – Distributing reads and writes across drives can significantly improve I/O speeds, especially in heavy workloads.
- Redundancy and reliability – Certain levels of RAID keep duplicate data, allowing continued access when disks fail.
- Simplified data backups – Backing up one large array can be easier than multiple separate drives.
For users that need high-capacity, high-speed storage for important data, RAID can be a beneficial solution. Media production teams working with huge video files often use RAID to improve workflow. Businesses may employ RAID to keep mission-critical data safe and accessible. For some home users, RAID provides peace of mind by reducing the risks of data loss.
Drawbacks and risks of RAID
Despite its advantages, RAID also carries some downsides to consider:
- Added cost – Building a RAID array requires purchasing multiple HDDs, as well as a controller for some setups.
- Complexity – Configuring and managing a RAID array requires technical expertise many users don’t have.
- Potential for downtime – If multiple drives fail in some RAID setups, data recovery can be difficult or impossible until failed drives are replaced.
- Slower writes – Many RAID levels incur a write penalty, meaning write speeds will be significantly slower than for standalone drives.
While RAID can provide redundancy, there remains a risk of unrecoverable data loss if critical configuration mistakes are made or multiple simultaneous drive failures occur. Some RAID levels are also vulnerable during rebuilding, when extra stress is placed on the array.
Do you need RAID?
Determining if RAID is right for your storage depends on considering these key factors:
- Your data storage and backup needs – If you have mission-critical or frequently accessed data, redundancy and performance may outweigh increased costs.
- Your budget – RAID arrays require buying multiple drives, and potentially other hardware. High-capacity hard drives already provide ample space for many users.
- Your technical expertise – Managing and troubleshooting RAID requires strong technical knowledge many users lack.
For home or small business users without huge storage needs, relying on external backups may provide more affordable protection. Online backup services provide redundancy without the RAID maintenance burden. But for some power users, RAID remains an appealing option.
What do you need for a RAID setup?
Should you decide to create a RAID array, you’ll need the following hardware:
- Two or more compatible HDDs – For best performance, all drives should have the same model, capacity and spindle speed.
- RAID controller – Can be dedicated hardware, or software integrated on motherboard. Controls configuration and distribution of data.
- Data cables – To connect HDDs to RAID controller ports.
- Available power connectors – HDDs will need sufficient power, supplied by PSU.
Many motherboards designed for performance PCs include onboard RAID controllers. This allows creating a RAID array without purchasing dedicated RAID cards. However, hardware controllers typically provide more advanced management features and better performance. Many external direct-attached RAID enclosures include their own hardware controller.
Choosing your RAID level
Once you have the necessary hardware, choosing your RAID level will depend on your priority for capacity, speed, or redundancy:
| RAID Level | Capacity | Read Speed | Write Speed | Fault Tolerance |
|---|---|---|---|---|
| RAID 0 | Total capacity of all drives | Very good | Very good | None |
| RAID 1 | Capacity of smallest drive | OK | Poor | Excellent |
| RAID 5 | (N-1) * Smallest capacity | Good | Poor | Good |
| RAID 6 | (N-2) * Smallest capacity | Good | Poor | Excellent |
| RAID 10 | Capacity / 2 drives | Very good | Good | Excellent |
Here, N is the total number of drives in the array. As this table demonstrates, there is always a trade-off – capacity, speed and redundancy cannot be maximized simultaneously. Prioritize what is most important for your needs.
Setting up your RAID array
Once hardware is in place, creating the RAID array requires configuring the RAID controller. This often involves accessing the controller’s configuration utility in the computer BIOS, but procedure varies by controller model. Key steps usually include:
- Select the RAID level you wish to use
- Select the physical disks to include in the array
- Initialize the array, which will write configuration data to disks
- Allow time for initialization to complete
- Check the status of the array to confirm functionality
Successfully creating the RAID array will provide access to the full consolidated capacity, with the performance benefits determined by your RAID level. The controller interface will often include tools to monitor the status of the array.
Expanding or migrating arrays
As storage needs grow over time, some RAID configurations allow for expanding capacity by adding disks. Migration to new arrays is also possible by moving data to a new set of disks, then swapping them into the controller in place of the old array. Always back up critical data before attempting any RAID configuration changes.
Maintaining and monitoring RAID
Like all storage systems, RAID arrays require ongoing maintenance and monitoring:
- Watch for warning signs like slow performance or unusual noises that can indicate issues.
- Check controller logs for any identified problems with drives.
- Keep firmware and drivers updated on controller and drives.
- Monitor drive S.M.A.R.T. data for signs of impending failure.
- Keep spare drives available for quick replacement if needed.
- Develop a recovery plan in case multiple drives fail.
While RAID can provide redundancy, drives will still fail eventually. Having smart monitoring and maintenance practices is essential to avoid losing access to data.
Is software RAID a viable option?
Software RAID controllers use system CPU and RAM resources instead of dedicated hardware. This avoids the cost of a RAID card, but comes with some key disadvantages:
- Consumes CPU cycles needed for other tasks
- No battery-backup cache, risking data loss on power failure
- Limited in available RAID levels and features
- Slower performance, especially under heavy load
Software RAID requires your system has spare CPU performance and RAM capacity to take on the RAID workload. Performance will still lag behind true hardware RAID. For simple setups in budget systems, software RAID can be workable. But for mission critical data, hardware RAID is preferable.
Choosing software vs. hardware RAID
| Software RAID | Hardware RAID | |
|---|---|---|
| Cost | None | Moderate to High |
| Performance | Low to Moderate | High |
| Reliability | Moderate | High |
| Ease of use | Difficult | Moderate |
| Features | Limited | Full |
For most uses, the benefits of true hardware-driven RAID make it preferable to software RAID.
Alternatives to consider
Though it remains a popular solution, RAID is not the only option for improving storage performance, capacity and reliability:
- Larger drives – Bigger HDDs and SSDs provide ample capacity without RAID complexity.
- Cloud storage – Services like Dropbox give redundancy through offsite data mirroring.
- External drives – USB hard drives make backups and transferring data easy.
- Newer technologies – Flash memory and cloud computing reduce reliance on local RAID.
In some use cases, these alternatives can provide simpler and more affordable solutions than RAID. As with any technology, RAID arrays have trade-offs to consider carefully.
Conclusion
RAID can provide performance, capacity and reliability improvements by combining multiple hard disk drives. But it carries a cost premium and requires technical expertise to implement successfully. For many home and small business users, external backups and new technologies like cloud storage present better data protection options.
In the end, your goals for data storage performance and redundancy will determine if RAID is a beneficial investment. Weigh your specific needs and willingness to manage a RAID system before deciding. While the right RAID setup can be a valuable asset, alternative storage solutions may prove more accessible and affordable in many cases.
