RAID (Redundant Array of Independent Disks) is a data storage technology that combines multiple disk drive components into a logical unit. RAID 6 is a type of RAID that provides fault tolerance by using two parity data strips distributed across the array. This allows the array to continue operating with up to two failed drives without losing data. Knowing what operating systems support RAID 6 can help you determine if it is an option for your storage needs.
What is RAID 6?
RAID 6 is a RAID configuration that uses block-level striping with double distributed parity. This means the data is broken down into blocks and striped across multiple drives in the array. Unlike RAID 5 which uses a single parity block, RAID 6 uses two parity blocks distributed across the member disks.
The double parity provides fault tolerance up to two drive failures. If one drive fails, the system can rebuild the data using the parity blocks. If a second drive fails before the first failed drive is replaced and rebuilt, the system can still operate and rebuild the data from the remaining good drives.
Because RAID 6 provides such a high level of fault tolerance, it is often used for mission critical data storage and applications where downtime cannot be tolerated. The tradeoff is lower storage efficiency since a portion of the overall capacity has to be reserved for the parity blocks.
Benefits of RAID 6
There are several key benefits that make RAID 6 a good option for systems that need maximum uptime and high capacity:
- High fault tolerance – Can withstand up to 2 drive failures without data loss
- Improved performance – Spreading I/O across multiple drives increases speed
- Capacity – Total array size is capacity of disks minus 2 for parity
- Rebuilding – Only failed drives need rebuilding versus full rebuild with RAID 5
For mission critical applications where downtime is unacceptable, the benefits of high fault tolerance and reduced rebuild times make RAID 6 a popular choice despite the additional cost.
Operating Systems That Support RAID 6
Many modern server and desktop operating systems include native software RAID capabilities that support RAID 6. Here are some of the most common options:
Windows has included software RAID support since Windows 2000 and Windows Server 2003. All modern versions including:
- Windows 10
- Windows Server 2019
- Windows Server 2016
- Windows 8/8.1
can configure RAID 0, 1, 5, and 6 arrays through the Windows Disk Management utility. The process involves selecting the physical disks you want to include, choosing to create a new volume, and selecting the RAID 6 option. This builds the array and formats the volume without requiring any third party tools.
The Linux MD driver supports RAID 0, 1, 4, 5, 6, 10 and can be used to create software RAID arrays. Support is included in most major distributions like:
- Red Hat Enterprise Linux
Configuration is done through command line tools like mdadm or graphical utilities like gnome-disks on GNOME desktops. Supported file systems include ext4, xfs, and btrfs.
macOS has included software RAID support since OS X Panther released in 2003. The Disk Utility application can be used to create RAID 0, 1, 5, and 6 arrays on both internal and external drives formatted with HFS+, APFS, or EXFAT.
Supported RAID levels on macOS include:
- RAID 0 – Striped set with no parity
- RAID 1 – Mirrored disks for 100% redundancy
- RAID 5 – Single parity stripe set
- RAID 6 – Double parity stripe set
FreeBSD includes the gvinum volume manager that supports RAID levels 0, 1, 5, and 6. Arrays can be created using the command line or via the GNOME gvinum utility on desktop installations.
Oracle Solaris has builtin support for hardware RAID controllers but can also configure software RAID 5 and 6 arrays. The Solaris Volume Manager (SVM) and ZFS file system both support RAID 6 virtual devices.
Hardware vs. Software RAID 6
RAID can be implemented via dedicated hardware RAID controllers or in software running on the host operating system. Both have their advantages:
- Better performance – Hardware RAID uses dedicated processors
- Operating system independent – Works the same regardless of OS
- RAID management built into controller BIOS
- Cost effective – Uses existing system resources
- Flexibility – Can be reconfigured without physical changes
- Supported natively by most operating systems
Software RAID provides a cost effective solution that is suitable for many applications. However, hardware RAID may be preferable for mission critical systems that require the best performance and reliability.
How to Choose Drives for RAID 6
When selecting drives for a RAID 6 array, there are several factors to consider:
- Drive capacity – Larger drives provide more total storage but have longer rebuild times if they fail.
- Drive interface – Faster interfaces like SAS and SATA SSD reduce rebuild time.
- Rotational vs SSD – SSDs have faster access times and lower latency.
- Drive reliability – Enterprise class drives designed for RAID have better reliability than consumer grade options.
For RAID 6, at least 4 physical drives are required but additional drives can be added to increase capacity and performance. Matching drives in terms of capacity, speed and type provides the most consistent performance across the array.
RAID 6 provides excellent fault tolerance through double distributed parity, allowing up to two drive failures with no data loss. It is supported through native software RAID included in most server and desktop operating systems as well as hardware RAID controllers.
When planning a RAID 6 implementation, consider hardware vs software RAID and choose drive capacity, interfaces, and reliability appropriate to your performance and capacity requirements.
With proper configuration using matching high quality drives, RAID 6 can deliver excellent performance and reliability for mission critical storage and virtualization applications that demand maximum uptime.
Frequently Asked Questions
What is the difference between RAID 5 and RAID 6?
The key difference is that RAID 5 uses single parity while RAID 6 uses double parity. This allows RAID 6 to continue operating with up to 2 drive failures compared to just 1 with RAID 5. However, the additional parity comes at a cost of lower total capacity and write performance.
Is software or hardware RAID 6 better?
Hardware RAID generally performs better thanks to dedicated parity calculation hardware. But software RAID can achieve excellent performance with modern multi-core CPUs. Software RAID is also easier to configure and offers more flexibility. For most applications, software RAID 6 is a very capable solution.
What is the minimum number of disks for RAID 6?
You need at least 4 drives for a RAID 6 array. This allows two drives for data striping, and two dedicated drives for the distributed parity information. For better performance, more data drives can be added.
Can RAID 6 use different size disks?
Technically yes, as the RAID array will use the smallest disk size as the base. However, this is not optimal as it leaves unused space on the larger disks. For best performance and utilization, all disks in a RAID 6 array should be identical in terms of capacity and speed.
Is RAID 6 worth the cost over RAID 5?
For mission critical data or applications where uptime is paramount, the additional fault tolerance of RAID 6 is worth the cost. The advantages are double parity, faster rebuild times, and higher IO performance during rebuilds. For less critical data, RAID 5 provides more space efficiency.