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How RAID Works: Comparing Common RAID Types

Redundancy is at the top of the pyramid when making data available as much as possible when stored on disk drives found on a locally hosted computer or a network-attached storage device. This is where RAID comes in as an option and how it works to potentially implement on a private server or on a bigger scale in a corporate network.

What is RAID and how it can be Implemented?

RAID stands for Redundant Array of Independent Disks which is a type of storage technology that combines a number of hard disk drives into a single logical disk in order for data to be distributed across every hard disk drive to guarantee performance and security.

The main goal of RAID is to combine multiple disk drives into an array that would display into one large logical storage unit to the storage server.

RAID can be implemented two ways via RAID controller with the ways being by a software RAID or through a hardware RAID.

Software RAID Method

software raid windows 10

Windows 10 offers the “Storage Spaces Management” feature that can be configured to implement both a RAID 0 and RAID 1 level configuration

The software RAID route can be implemented on a server by using third-party software that groups multiple disks onto a virtual disk.

Besides configuring RAID on third-party software, RAID can be implemented on Windows 10 or other operating system by going through the “Manage Storage Spaces” feature to setup a software-type RAID.

RAID arrays implemented over software does use CPU resources as used within the operating system which makes it simply a low-cost option compared to a hardware RAID implementation; but, does compromise read/write performance.

Software RAIDS do not need additional hardware to be implemented and compatibility of RAID drivers can be used across the same supported operating system type on a majority of other systems that support the RAID controller being used.

However, software RAIDs cannot be implemented on disk partitions across other operating systems. For Example: Software RAID and partitions implemented on Windows operating systems cannot be shared on a Linux OS, the partition can only be seen on Windows OS and Windows-supported device.

Besides performance downsides, software RAIDs are more limited to the point that only RAID 0 and RAID 1 are the only options to use while RAID 5 and higher RAID levels are unavailable due to performance restrictions that prevent software RAIDS from supporting the higher RAID levels.

Hardware RAID Method

raid controller card

Part of the Hardware RAID implementation, a RAID controller like the StarTech 4x SATA PCIe RAID controller can be implemented to configure a RAID

A Hardware RAID configuration is completely the opposite as what is mentioned about software RAIDS since hardware RAIDS use physical hardware RAID controllers that are physical cards added to an existing storage server to benefit in using little to no CPU resources.

How a hardware RAID works is that it allows system and network administrators to boot straight to the RAID controller via a configuration utility made available by the manufacturer of the RAID controller in order to configure the RAID levels.

The most important benefit of the Hardware RAID method is that it allows disk drives to be “hot-swappable” and won’t interrupt or terminate the RAID configuration when there is a disk failure as long as the RAID being used has the minimal drives still active.

Hardware RAIDs are more expensive due to additional hardware in the form of multiple storage servers and multiple RAID cards needed to maintain performance, the overhead and maintenance requirement does increase when RAID controllers fail which means finding a compatible RAID controller to replace the one that has failed.

Overall, a Hardware RAID is the best method of RAID because of it’s easy integration with any server/host operating system and provides better efficiency in error recovery when there is a sudden power glitch or other hardware failure that takes a network offline.

How RAID Works in Each RAID Level?

Now that we’ve briefly explained how RAID works and the two ways RAID can be configured through hardware or software methods, the next section will explain 6 types of RAID levels that are available to choose from that can be implemented based on performance, reliability, and costs factors.

The 6 RAID levels to be discussed includes RAID 0, RAID 1, RAID 1+0, RAID 0+1, RAID 5, and RAID 6 options along with how striping and mirroring are used in each of the 6 levels.

RAID 0 Level

raid 0 diagram

Starting out with a configuration focused on performance, RAID 0 is the entry-level configuration of RAID where it requires a minimum of 2 disk drives to be functional.

RAID 0 strips across disk drives in the array by accessing disks at the same time instead of one disk at a time and then splits data up into multiple blocks.

With RAID 0, there is no fault tolerance meaning that if any of the drives fails then the whole RAID configuration will be taken down permanently; but, is beneficial for backing up noncritical data that requires high performance write speeds.

RAID 1 Level

raid 1 diagram

Completely the opposite of RAID 0, the RAID 1 level uses “mirroring” disk sets which allows the RAID to be configured to copy data on the disk drives by copying data found on disk 1 and placing it on the disk 2.

Just like RAID 0, RAID 1 requires a minimum of 2 disk drives to create a volume partition and RAID array.

How RAID 1 work is it force read requests to be serviced by both disk 1 and disk 2 while forcing write requests to update both disks at the same time when data is modified or added to disk 1.

The major difference between RAID 0 in the case of RAID 1 is that RAID 1 does have fault tolerance where the RAID configuration will not be affected when a single disk drive fails; but, it still does not protect against data corruption or deletion since the changes would take affect on other mirrored disks in the array.

In any instance when data corruption or disk controller failure occurs in RAID 1, a rebuild of the RAID at this level is always a possibility or in other instances a backup plan where higher RAID levels would prevent a RAID rebuild.

RAID 1+0 Level

raid 10 diagram

Also known as “RAID 10”, RAID 1+0 is a mixture of both RAID 0 and RAID where it provides both striping and mirroring (in other ways performance and data protection benefits) with a majority of the RAIDs being 2 or more RAID 1 arrays in a top-level RAID 0 array.

When a single drive fails in RAID 10, the lower-level mirrored drives will enter into degradation mode while the top-level striped drive will still perform normally without taking the RAID down at all since there is a minimum of 4 drives required for RAID 10 to work properly.

Despite performance and data protection being beneficial in RAID 10, it has the minor disadvantages of cutting storage space by 50% due to the lower disk drives being reserved for disk mirroring and it is not a cheap RAID configuration to implement.

RAID 10 is common in high input/output storage environments common with application and database servers that requires 24/7 availability and constant writing updates within SQL records and scripts on the backend.

RAID 0+1 Level

raid 0 1 diagram

Opposite of RAID 10, RAID 0+1 is another nested RAID type where the (also referred as “RAID 01”) arrays are made up of a top-leveled RAID 1 mirrored disk containing 2 or more RAID 0 striped disk sets.

RAID 01 does have fault tolerance; but it does have a disadvantage of longer recovery in comparison to RAID 10 since one of the lower-level striped disks may fail and will require the stripped set to be rebuilt from an empty set after the mirrored set is rebuilt on the empty stripe set.

On the plus side, the top-level mirrored set would remain to operate normally so data would still be available to be accessed.

RAID 01 can be used the same way for high performance and reliability as far as I/O used in storage servers; but, it will require more hands-on maintenance. Just like RAID 10, it requires a minimum of 4 drives to be operational.

RAID 5 Level

raid 5 diagram

Moving from the 2 common nested RAID levels to one of the most common standard RAID levels, RAID 5 provides a balance of performance, data protection, and the costs.

How RAID 5 works is that it uses block-level striping for performance benefits while it pairs striping with distributed parity data used in playing a role for data protection by distributing the parity along with all data across all disk drives.

When a failed drive has been replaced with a new disk drive in the RAID 5 level, the parity data in the array plays a role in rebuilding the missing data from the failed drive back onto the new drive. This is the process of placing a new disk drive in data recovery mode.

RAID 5 requires 3 disk drives to be configured and has a fault tolerance of allowing 1 disk drive to fail before the RAID array fails to operate any longer.

RAID 6 Level

raid 6 diagram

The final RAID level to mention is the RAID 6 which is the same as far as striping and parity block usage; but, it is considered slightly different than RAID 5.

RAID 6 upgrades from RAID 5 by going from single parity distribution block to a double-parity distribution block that is distributed across each of the 4 disk drives RAID 6 for it to be operational.

The added benefit RAID 6 has is that it doubles fault tolerance from 1 disk drive failure to a 2 disk drive failure

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