RAID Configurations and Concepts
Drive Redundancy and RAID
Introduction
Hard drives, SSDs, and other storage devices are used to store large amounts of important information.
Data loss is a concern due to the physical nature of these devices, which have constantly moving components.
Failure of any component can render all data on the drive inaccessible.
Redundancy can be created by combining multiple drives.
RAID (Redundant Array of Independent Disks) is not a backup solution; a separate backup process is still necessary.
RAID Definition
RAID stands for Redundant Array of Independent Disks (sometimes also referred to as Redundant Array of Inexpensive Disks).
It involves different methods to implement redundancy.
Some RAID methods provide redundancy even if a drive is lost, while others do not.
RAID Levels
RAID 0 (Striping)
RAID 1 (Mirroring)
RAID 5 (Striping with a single Parity Drive)
RAID 6 (Striping with two Parity Drives)
Nested RAID (RAID 10 or RAID 1+0, Stripe of Mirrors)
RAID 0 (Striping)
Requires at least two physical drives.
Data is split across multiple storage devices.
A single file is divided into multiple parts, with each part stored on a different drive.
Example: Drive 1 has Block 1A, Drive 2 has Block 2A, Drive 1 has Block 3A, and so on.
Known for its speed because data is written to multiple drives simultaneously.
Losing one drive results in data loss due to the unavailability of parts of the file.
RAID 0 has zero redundancy.
RAID 1 (Mirroring)
Requires at least two drives.
Data is duplicated across multiple drives.
Disk 0 has an exact duplicate of the information on Disk 1.
Requires twice as much storage space to store the same information.
If a drive fails, the other drive containing the exact duplicate of the data remains available.
The failed drive should be replaced, and the mirror recreated but data remains accessible during this process.
RAID 5 (Striping with Parity)
Uses parity to provide redundancy.
Striping is similar to RAID 0, where a file is split into pieces and distributed across multiple drives.
The last drive contains parity data, not file data.
In a RAID 5 array with four drives, three drives store data, and one stores parity data.
Parity is distributed across multiple physical drives to make the recovery process more efficient.
Doesn't require duplicating all data, thus saving drive space.
If a drive fails, the data can be recreated using the remaining data and parity information.
Parity calculation requires CPU overhead, which causes performance impact during recovery.
RAID 6 (Striping with Dual Parity)
Similar to RAID 5 but adds an additional storage drive with an additional parity block.
Can withstand the failure of two drives.
If one drive fails, it functions like RAID 5.
If two drives fail, the lost data can be recreated using the existing parity data.
Losing two physical drives in a RAID 6 array still allows access to all data.
Requires a separate physical drive to store the additional parity data.
It does not add additional capacity, only redundancy.
RAID 10 (RAID 1+0, Stripe of Mirrors)
Combines RAID 0 (Striping) with RAID 1 (Mirroring).
With RAID 0, a single file is split into blocks and distributed across multiple drives.
RAID 0 has zero redundancy, so losing a drive results in data loss.
RAID 1+0 adds mirroring to the striped set of drives.
Requires at least four drives.
Each striped set of drives is mirrored onto separate drives.
Can withstand the loss of multiple drives and still remain operational.
For example, in one scenario, losing one drive per mirror still keeps the system running.
Practical Considerations and Redundancy Cost
RAID 0:
No redundancy
All disk space is usable
If you have two 5TB drives that is 10 TB of available space
RAID 1:
Fault tolerance of 1/2 (one half)
If you have 20 TB, using all 5 TB sizes, you will only be able to save 10 TB of files.
RAID 5:
Needs a minimum of three drives.
Loses one disk space to the parity.
If you have 5 by 4, you will only get 15 as one gets dedicated for party.
RAID 6:
Needs a minimum of four drives.
Two disks get dedicated to party.
RAID 10:
Must have a multiple of 4 to create the sets of mirrors.
It's expensive as you must lose half the space for redundancy.
Questions and Parity Explained
Once setup RAID is automatic.
RAID is usually about creating redundancy in disk so that if one disc or disk fails, it can rebuild.
RAID can just rebuild itself.
Parity is a mathematical computation that is applied that gives the parity bit.
Parity bits allow you to rebuild your array by acting like a magic spell that can do calculations.
With parity, instead of a physical copy, you are making a tiny little copy with that parity. You will need more space for the parity bit to work from
Parity is distributed throughout the arrays.
With Distributed parity, not one disc has decided to be the parity disc, but instead, all discs have parity in them.
Fault tolerance means how many arrays can I or how many disk can I lose in my system still function.
Hot Swappable means I can switch it while the system is still on.
Minimum Disc: Raid has to have a minimum disc and with RAID 0, that number is 2.
Final Words
Study RAID as it can show up on test and be a PBQ.
Introduction
Hard drives, SSDs, and other storage devices store large amounts of important information.
Data loss is a concern due to the physical nature of these devices, which have constantly moving components and magnetic platters that can degrade over time.
Component failure can render all data on the drive inaccessible. This includes electronic components and mechanical parts.
Redundancy can be created by combining multiple drives into a single logical unit.
RAID (Redundant Array of Independent Disks) is not a backup solution; a separate backup process is still necessary to protect against data loss due to other types of failures.
RAID Definition
RAID stands for Redundant Array of Independent Disks (sometimes also referred to as Redundant Array of Inexpensive Disks).
It employs various methods to implement redundancy, which can include mirroring, striping, and parity.
Some RAID methods provide redundancy even if a drive is lost, while others do not, making it essential to choose the right RAID level for your needs.
RAID Levels
RAID 0 (Striping)
RAID 1 (Mirroring)
RAID 5 (Striping with a single Parity Drive)
RAID 6 (Striping with two Parity Drives)
Nested RAID (RAID 10 or RAID 1+0, Stripe of Mirrors)
RAID 0 (Striping)
Requires at least two physical drives to operate.
Data is split across multiple storage devices to increase performance.
A single file is divided into multiple parts, and each part is stored on a different drive.
Example: Drive 1 has Block 1A, Drive 2 has Block 2A, Drive 1 has Block 3A, and so on, allowing for parallel read and write operations.
Known for its speed because data is written to multiple drives simultaneously, effectively multiplying the read and write speeds.
Losing one drive results in data loss due to the unavailability of parts of the file, making it unsuitable for critical data.
RAID 0 has zero redundancy, meaning there is no fault tolerance.
RAID 1 (Mirroring)
Requires at least two drives to create a mirror.
Data is duplicated across multiple drives, providing complete redundancy.
Disk 0 has an exact duplicate of the information on Disk 1, ensuring data availability in case of a drive failure.
Requires twice as much storage space to store the same information, effectively halving the usable storage capacity.
If a drive fails, the other drive containing the exact duplicate of the data remains available, allowing for continuous operation.
The failed drive should be replaced, and the mirror recreated, but data remains accessible during this process with minimal downtime.
RAID 5 (Striping with Parity)
Uses parity to provide redundancy without fully duplicating the data.
Striping is similar to RAID 0, where a file is split into pieces and distributed across multiple drives.
The last drive contains parity data, not file data, which is calculated from the data on the other drives.
In a RAID 5 array with four drives, three drives store data, and one stores parity data, distributed in a rotating manner.
Parity is distributed across multiple physical drives to make the recovery process more efficient and balanced.
Doesn't require duplicating all data, thus saving drive space compared to RAID 1.
If a drive fails, the data can be recreated using the remaining data and parity information, ensuring data availability.
Parity calculation requires CPU overhead, which causes performance impact during recovery, potentially slowing down the system.
RAID 6 (Striping with Dual Parity)
Similar to RAID 5 but adds an additional storage drive with an additional parity block, providing enhanced fault tolerance.
Can withstand the failure of two drives simultaneously without data loss.
If one drive fails, it functions like RAID 5, using the remaining data and parity to maintain operation.
If two drives fail, the lost data can be recreated using the existing parity data from the other drives.
Losing two physical drives in a RAID 6 array still allows access to all data, making it suitable for critical systems.
Requires a separate physical drive to store the additional parity data, reducing the overall usable storage capacity.
It does not add additional capacity, only redundancy, ensuring data protection.
RAID 10 (RAID 1+0, Stripe of Mirrors)
Combines RAID 0 (Striping) with RAID 1 (Mirroring) to offer both performance and redundancy.
With RAID 0, a single file is split into blocks and distributed across multiple drives, increasing read and write speeds.
RAID 0 has zero redundancy, so losing a drive results in data loss, which is mitigated by the mirroring in RAID 10.
RAID 1+0 adds mirroring to the striped set of drives, creating a highly available and fast storage solution.
Requires at least four drives to implement, with each pair of drives forming a mirrored set.
Each striped set of drives is mirrored onto separate drives, providing redundancy and improving performance.
Can withstand the loss of multiple drives and still remain operational, depending on which drives fail.
For example, in one scenario, losing one drive per mirror still keeps the system running, ensuring high availability.
Practical Considerations and Redundancy Cost
**RAID 0:** - No redundancy
All disk space is usable
If you have two 5TB drives that is 10 TB of available space
**RAID 1:** - Fault tolerance of 1/2 (one half)
If you have 20 TB, using all 5 TB sizes, you will only be able to save 10 TB of files.
**RAID 5:** - Needs a minimum of three drives.
Loses one disk space to the parity.
If you have 5 by 4, you will only get 15 as one gets dedicated for party.
**RAID 6:** - Needs a minimum of four drives.
Two disks get dedicated to party.
**RAID 10:** - Must have a multiple of 4 to create the sets of mirrors.
It's expensive as you must lose half the space for redundancy.
Questions and Parity Explained
Once setup RAID is automatic, managed by the RAID controller.
RAID is usually about creating redundancy in disk so that if one disc or disk fails, it can rebuild, ensuring data integrity.
RAID can just rebuild itself, often in the background, without interrupting system operations.
Parity is a mathematical computation that is applied that gives the parity bit, used to reconstruct lost data.
Parity bits allow you to rebuild your array by acting like a magic spell that can do calculations, restoring the data.
With parity, instead of a physical copy, you are making a tiny little copy with that parity. You will need more space for the parity bit to work from
Parity is distributed throughout the arrays, enhancing fault tolerance.
With Distributed parity, not one disc has decided to be the parity disc, but instead, all discs have parity in them, improving performance.
Fault tolerance means how many arrays can I or how many disk can I lose in my system still function, indicating the system's resilience.
- Hot Swappable means I can switch it while the system is still on, minimizing downtime.
Final Words
Study RAID as it can show up on test and be