Home Server/RAID

Warning: RAID is NOT a backup. Not even RAID 1. RAID doesn't protect against accidental file deletion or the complete death of an array. See the Home_Server/Backups Page for more on backups

Companion page to Home_server#RAID

There are several reasons why we don't just connect a bunch of disks and call it good:

Data Protection: RAID provides redundancy, which means that if one disk fails, the data is still available on another disk. This is crucial for preventing data loss.

Performance: RAID can significantly improve disk speed by spreading data across multiple disks. This allows for multiple disk reads/writes to occur simultaneously, increasing overall system performance.

Scalability: RAID systems can be easily expanded with additional disks, providing a scalable solution for growing storage needs.

In contrast, if you simply connect a bunch of disks separately (disk A for pictures, disk B for videos), you lose these benefits. If one disk fails, you lose all data on that disk. You also can't take advantage of the speed benefits of simultaneous reads/writes across multiple disks.

RAID Levels

RAID is a method of storing the same data in different places on multiple hard disks to protect data in the case of a drive failure.

There are several different RAID levels, each with its own method of data distribution across the drives. The most common are RAID 0, RAID 1, RAID 5, RAID6, and RAID 10.

RAID 1 is known as mirroring. It duplicates the same data on two or more disks. This means if you have two 1TB drives in a RAID 1 setup, you only get 1TB of storage, not 2TB. This is because the same information is written to both drives for redundancy. So, the storage efficiency is 50%.

RAID 5 uses striping with parity. It requires at least three disks, but it provides a balance of good performance, good fault tolerance, and high capacity and storage efficiency. In RAID 5, data and parity (which is a form of error checking) are striped across three or more drives. If a single drive fails, the original data can be reconstructed from the remaining data and the parity data. However, some space is used for this parity information, so you don't get 100% of the total storage. RAID 5 is no longer recommended for critical data storage.

RAID 6 is an extension of RAID 5, and it provides more redundancy than RAID 5 by using an additional parity block. This means that RAID 6 can withstand the failure of two drives in the array without any data loss, while RAID 5 can only withstand the failure of one drive. RAID 6 requires a minimum of four drives and the storage efficiency is lower because more space is used for parity data. Also, the performance of RAID 6 can be slower than RAID 5, especially for write operations, because the system has to calculate and write two sets of parity data. If this is a concern, use RAID 10.

RAID 10 is a combination of RAID 1 and RAID 0, and it requires a minimum of four disks. It provides the redundancy of RAID 1 along with the increased performance of RAID 0. You typically get only 50% of the total storage in a RAID 10 array, but the trade-off is increased data protection and increased performance. RAID 10 is the go-to choice for professional applications.

Don't get greedy and prioritize storage efficiency over redundancy and reliability. RAID systems are designed to protect data from hardware failure, but if you attempt to maximize storage at the cost of redundancy, you risk losing your data. Sacrificing redundancy for more storage space can lead to catastrophic data loss.

ZFS

ZFS is a .... Home_Server/RAID/ZFS