RAID 6: Comprehensive Guide to Minimize Data Loss
RAID 6 is one of the most popular RAID levels used in big data environments. It offers high fault tolerance and redundancy, thanks to its support for double parity drive. However. Even though RAID 6 offers high tolerance, it does so at the expense of data speed – RAID 6 is one of the RAID levels with slow write performance.
But then, this RAID level is ideal for several use cases. In this article, we will explain the RAID 6 array and how it functions. This article also touches on other similar RAID levels such as RAID 5 and RAID 10, while highlighting the best approach to recovering data from a failed RAID, even if the RAID controller is damaged.
What is RAID 6?
RAID 6 is a RAID level that supports data striping – just as with RAID 0 – with dual parity. This RAID level shares many similarities with RAID 5 in that it supports dedicated parity drives and data striping. But unlike RAID 5, the dedicated parity drive on RAID is double, so the RAID can withstand up to 2 simultaneous disk failures. You need a minimum of four drives to set up RAID 6.
How Does RAID 6 Work?
RAID 6 borrows the data striping feature of RAID 0 and adds parity distribution to infuse redundancy and fault tolerance. In RAID 6, new data is received into the array and striped into bits; each bit is saved uniquely across the data drives in the array, while parity information is distributed across the parity drives.
Due to this seemingly long procedure, RAID 6 delivers slow write speeds. But when the data is being accessed, the read speed is decent, especially for bulk data. In RAID 6, if one drive fails, the array will automatically rebuild itself if you replace the failed drive; the new drive will be rebuilt using the data saved on the parity drives.
The data drives are the actual drives where data is saved in a RAID 6 array, while the parity drives are the drives that store parity information.
RAID 6 does not allow you to utilize up to 85% of your data drives; the total storage capacity you get from RAID 6 is calculated using this formula:
Formula: (Number of hard drives in the array: 2) x capacity of the smallest drive in the array.
So, let’s say you have six 500 GB drives to use for the array, the capacity you would get is (6 – 2) x 500 GB, which will give us 2 TB. So, instead of 3 TB of space, you will only get 2 TB from the six drives. Well, actually, the “lost” 1 TB would be used for storage parity information. The “2” being subtracted in the formula refers to the dedicated parity drives.
Features of RAID 6
- Distributed Parity: RAID 6 distributes parity data across the dedicated parity drives in the array. This serves for data loss prevention and hot swaps in the case of drive failure.
- High Fault Tolerance: Unlike many other RAID levels, RAID 6 can withstand two drive failures at a go, and would rebuild automatically once the drives are replaced.
- Good Storage Space: RAID 6 actually lets you use a reasonable amount of the total storage for all drives in the array.
- Minimum Requirement: You need at least four disks to configure this RAID level.
Performance of RAID 6
RAID 6 isn’t the fastest RAID level in terms of performance; its write speed is slow since it needs to write dual parity data and distribute it across the dedicated parity drives. But the read speed is decent. Overall, RAID 6 delivers an excellent read and write speed – but not to compare with RAID 10, RAID 0, and RAID 5 (these ones are faster).
RAID 0 is the fastest RAID level because it does not support any form of parity (zero fault tolerance); RAID 5 performs a bit faster than RAID 6 because it only uses one parity drive whereas RAID 6 uses two; and RAID 10? The performance is close to that of RAID 0 since it is a nested RAID level that combines RAID 1 pair into a RAID 0 configuration.
Pros and Cons of RAID 6
Pros
- High Fault Tolerance: RAID 6 can tolerate up to two simultaneous drive failures. This makes it more reliable than RAID 5, which can only tolerate one drive failure.
- Improved Data Security: The double parity in RAID 6 provides enhanced data security compared to RAID 5, ensuring data integrity even if two disks fail.
- Good Read Performance: RAID 6 offers good read performance, making it suitable for environments where read operations are more frequent than write operations.
- Scalability: RAID 6 arrays can be expanded by adding more disks, providing flexibility and scalability for growing storage needs.
- Efficient Storage Utilization: While RAID 6 uses more storage for parity compared to RAID 5, it still provides a good balance between fault tolerance and usable storage space.
Cons
- Slower Write Performance: The process of calculating and writing double parity information can slow down write operations, making RAID 6 less suitable for write-intensive applications.
- Higher Complexity: RAID 6 is more complex to implement and manage compared to simpler RAID levels, requiring more advanced controllers and management tools.
- Increased Cost: The need for additional drives and more sophisticated RAID controllers can increase the cost of a RAID 6 setup compared to other RAID configurations like RAID 0 or RAID 1.
- Rebuild Time: Rebuilding a failed RAID 6 array can be time-consuming and may impact performance during the rebuild process, especially with large-capacity drives.
- Power Consumption: The increased number of drives in a RAID 6 array leads to higher power consumption, which can be a concern in large-scale deployments.
RAID 6 offers a robust solution for environments that require high fault tolerance and data security, particularly in read-intensive applications. However, its slower write performance, complexity, and higher cost might make it less suitable for certain use cases. When considering RAID 6, it's important to weigh these pros and cons based on specific storage needs and performance requirements.
Note: RAID 10 vs RAID 6Applications of RAID 6
1. Data Warehousing: RAID 6 is well-suited for data warehousing applications where large volumes of data are stored and accessed. The high fault tolerance ensures data availability, and the good read performance allows for efficient data retrieval.
2. Archival Storage: For long-term data storage and archiving, RAID 6 provides the necessary redundancy to protect against data loss. Its ability to handle multiple drive failures is crucial for preserving historical data.
3. Backup Solutions: RAID 6 is commonly used in backup systems where data integrity and reliability are paramount. The double parity mechanism ensures that backup data remains safe even in the event of multiple disk failures.
4. Media and Content Libraries: In environments that store large media files such as video, audio, and high-resolution images, RAID 6 offers the fault tolerance and storage capacity needed to manage and protect these valuable assets.
5. Virtualization: Virtualized environments benefit from RAID 6's balance of performance and fault tolerance. It ensures that virtual machines (VMs) remain operational even if two disks fail, providing a stable platform for hosting multiple VMs.
6. Enterprise File Servers: RAID 6 is ideal for enterprise-level file servers where large amounts of data are accessed and modified by multiple users. Its ability to handle read-intensive operations and provide data redundancy makes it a reliable choice.
7. Scientific and Research Computing: In scientific and research fields, large datasets are common, and data integrity is critical. RAID 6 offers the necessary protection and storage capacity to support these data-intensive applications.
8. Financial and Banking Systems: Financial institutions require high levels of data integrity and availability. RAID 6 ensures that transaction data and financial records are safeguarded against multiple drive failures, maintaining the reliability of critical systems.
9. Cloud Storage: RAID 6 can be used in cloud storage infrastructures to provide robust data protection and redundancy. It helps ensure that cloud-based data remains available and secure, even in the event of hardware failures.
10. Business Continuity Planning: Organizations that prioritize business continuity can utilize RAID 6 to ensure data availability and minimize downtime. Its high fault tolerance supports the seamless operation of critical business applications.
RAID 6 is an excellent choice for applications that require high levels of data protection, fault tolerance, and storage capacity. Its ability to handle multiple drive failures makes it a reliable option for various industries, including data warehousing, archival storage, backup solutions, media libraries, virtualization, enterprise file servers, scientific research, financial systems, cloud storage, and business
How to Configure RAID 6?
Step-by-Step Guide to Configuring RAID 6:
1. Plan and Prepare:
- Determine Requirements: Identify the storage capacity, performance needs, and the number of drives required.
- Backup Data: Ensure that all important data is backed up before starting the configuration process.
- Select RAID Controller: Choose a RAID controller that supports RAID 6. This can be a hardware RAID controller or software RAID solution.
2. Gather Hardware:
- Disks: You need at least four hard drives or SSDs for RAID 6.
- RAID Controller: Ensure your RAID controller is installed and configured in your system.
3. Install RAID Controller (if using a hardware RAID):
- Insert the RAID Controller Card: Power off the computer and install the RAID controller card into the appropriate slot.
- Connect Drives: Connect the hard drives to the RAID controller using the appropriate cables.
4. Access RAID Configuration Utility:
- Boot into RAID BIOS/UEFI: Restart the computer and enter the RAID configuration utility, typically accessed by pressing a specific key during startup (e.g., Ctrl+R, Ctrl+I, or a key specified by the RAID controller manufacturer).
5. Create RAID 6 Array:
- Select Drives: In the RAID configuration utility, select the drives you want to include in the RAID 6 array.
- Choose RAID Level: Select RAID 6 as the RAID level.
- Configure Settings: Set the stripe size, parity type, and other RAID parameters as required. Default settings usually work well for most scenarios.
- Initialize Array: Start the initialization process to create the RAID 6 array. This may take some time, depending on the size of the drives.
6. Install Operating System (if not already installed):
- Load RAID Drivers: If you are installing an operating system, you may need to load RAID drivers during the OS installation process. These drivers are typically provided by the RAID controller manufacturer.
- Partition and Format: Partition and format the RAID 6 array as required by the operating system.
7. Configure RAID 6 in Software (if using software RAID):
- Linux (mdadm):
- Install
mdadm:sudo apt-get install mdadm(for Debian-based systems) orsudo yum install mdadm(for Red Hat-based systems). - Create the RAID 6 array:
sudo mdadm --create /dev/md0 --level=6 --raid-devices=4 /dev/sd[b-e]1 - Save the configuration:
sudo mdadm --detail --scan >> /etc/mdadm/mdadm.conf - Create a filesystem:
sudo mkfs.ext4 /dev/md0 - Mount the array:
sudo mount /dev/md0 /mnt
- Install
- Windows (Storage Spaces):
- Open "Server Manager" and navigate to "File and Storage Services."
- Select "Storage Pools" and create a new pool using the available drives.
- Create a new virtual disk in the pool, selecting "Parity" (equivalent to RAID 6).
- Format the new virtual disk with the desired file system.
8. Monitor and Maintain:
- RAID Management Software: Use the RAID controller's management software or operating system tools to monitor the health of the RAID array.
- Regular Backups: Continue to perform regular backups even with the added redundancy of RAID 6.
- Check for Errors: Periodically check for and address any errors or issues reported by the RAID management software.
What Happens When RAID 6 Configuration Fails?
It is always advisable to create RAID levels using brand-new hard drives or formatted old drives with no data stored on them. This is because creating a RAID would wipe any existing data on the selected RAID data drives.
Also, after you’re done setting up a RAID, it is important that you regularly back up every new data that goes into the RAID storage. While RAIDs may offer fault tolerance, they don’t substitute for backups – a RAID array may fail for quite many reasons, and if your data isn’t backed up, you’ll be in a mess.
For RAID 6, if there are just two failed drives, you should simply replace them and the array will rebuild automatically. If there are more than 2 failed drives at a go, you will need the assistance of a RAID recovery solution (if there’s no backup to recover from)). DiskInternals RAID Recovery software is software to think of when considering a reliable RAID recovery program to help out.
What Other Common RAID Levels Are There?
RAID 6 is not the only commonly used RAID level, in fact, it is the least preferred. Other better alternative RAID levels include:
- RAID 0: Uses bit-level data striping with zero tolerance; once drive failure will shut down the entire storage.
- RAID 1: Uses mirroring technique to same the same data block across all drives in the array. Until the last drive in the array fails, you can still access your full data from the RAID.
- RAID 5: Supports block-data striping with a dedicated parity drive for hot swaps. In the case of a single drive failure in the array, RAID 5 will rebuild automatically.
RAID 10: Supports both data striping and mirroring due to the nested RAID 1 and RAID 0.
FAQ
What is RAID 6 in simple terms?
RAID 6, also known as double-parity RAID, is a RAID scheme that places data across multiple disks, allowing I/O operations to overlap and thus enhance performance. Unlike some other RAID types, RAID 6 provides redundancy, ensuring data protection even if two disks fail simultaneously.
What's the difference between RAID 5 and 6?
The main distinction between RAID 5 and RAID 6 is that RAID 5 can continue operating after a single disk failure, while RAID 6 can withstand two simultaneous disk failures and still remain functional. Additionally, RAID 6 arrays are less likely to encounter errors during the disk rebuilding process.
How many drives are in RAID 6?
RAID 6 requires a minimum of 4 drives and a maximum of 32 drives to be implemented. Usable capacity is always two less than the number of available drives in the RAID set.
What are the advantages of RAID 6?
RAID 6 offers a blend of optimal storage capacity, strong security, and reliable performance. It is ideal for scenarios where data availability and fault tolerance are crucial, such as enterprise storage systems, database servers, and large video file storage.