What RAID storage mode is best for a surveillance recorder?

RAID stands for “Redundant Array of Independent Disks,” which refers to an array of redundant disks constructed according to specific requirements. In an operating system, these multiple disk drives appear as a single large storage device.

RAID is divided into different levels based on various needs and design requirements. When data needs to be stored, it must first be processed according to the RAID system’s specifications, which primarily involves adding redundancy information. This new data, along with the redundancy information, is then stored in the disk array.

Uses of RAID:

As a storage device composed of multiple working devices, RAID can take full advantage of its multiple storage devices. It can improve storage speed and increase capacity, while also providing fault tolerance and disaster recovery. With the use of redundancy information, it effectively protects data from being lost due to the failure of a single storage device. Some RAID levels can continue to operate even when multiple storage units fail.

Common RAID Levels: RAID0, RAID1, RAID5, RAID10

1. RAID0:
   • Characteristics: No redundancy or parity, requires at least two hard drives. It combines the drives into one, spreading data across all drives. Because the bandwidth is doubled, the read and write speed is also doubled. The theoretical speed of RAID0 is N times that of a single drive, but since the data is distributed across multiple drives, the security is reduced by N times. Any single drive failure results in the loss of all data.
   • Features: Simply improves read/write performance without providing any guarantee of data reliability. RAID0 is the most fragile of all RAID configurations. It has no redundancy, and failure of any single drive affects all data. RAID0 is not suitable for environments with high data security requirements.
2. RAID1:
   • Characteristics: A secure RAID mode that implements redundancy through disk mirroring. Data is mirrored on two drives, creating a backup of the data on each. When one drive fails, data can still be read from the other.
   • Features: RAID1 is the most costly in terms of storage space but provides high data security and availability. If one drive fails, the system automatically switches to the mirrored disk for reading and writing without the need to rebuild failed data. If the first failed drive is not replaced in time and the second drive also fails, RAID1 will fail. In most cases, data can be fully recovered by using the second drive, which contains the complete data.
3. RAID5:
   • Characteristics: The most widely used RAID level, requiring at least three drives. It balances data security and storage space utilization. Data is read from the parity blocks, so the failure of one drive does not cause service interruption.
   • Features: RAID5 is suitable for archival purposes and environments that require high performance and continuous data access (such as video editing). If a physical disk fails, its data can be rebuilt onto a replacement disk. Data will not be lost with the failure of a single disk, but if another disk fails before rebuilding is complete, all data will be lost. RAID5 has good read performance, but write performance is slightly slower due to parity calculations and writing.
   • Storage Capacity: The total logical capacity is the sum of all physical disks minus one physical disk’s capacity.
4. RAID10:
   • Characteristics: A combination of RAID1 and RAID0. It is a structure designed to complement the strengths and weaknesses of RAID1 and RAID0, achieving both security and speed.
   • Features: RAID10 requires at least four hard drives. It provides the extraordinary speed of RAID0 and the high data reliability of RAID1, but disk utilization is relatively low. RAID10 is mainly used for small capacity environments that require high speed and fault tolerance, such as databases. RAID10 is composed of multiple RAID1 groups forming a RAID0. It allows one member disk of each RAID1 group to be offline. If one member disk of a RAID1 group fails, the system continues to function, but the RAID10 will fail if both disks in the same RAID1 group fail.

RAID Usage Suggestions:

1. RAID0: Suitable for environments where high read/write speed is required but data security is not a primary concern. RAID0 is the most fragile RAID type, as any disk failure can result in data loss.
2. RAID1: Recommended for environments where data security is a high priority and disk read/write speed is not as critical.
3. RAID5: Recommended for environments where both data security and read/write speed are important. RAID5 is commonly used for storage and archiving purposes.
4. RAID10: Recommended for environments requiring high performance and high data reliability, but it has lower disk utilization efficiency.

Hard Disk Selection Recommendations:

• It is recommended to use hard drives from the same brand to reduce performance differences.
• For RAID1, RAID5, and RAID10 configurations, it is best to use hard drives with the same capacity and model to maximize the utilization and performance of the drives.

In surveillance storage systems, stability and reliability are paramount, and speed is less critical. Therefore, RAID5 is commonly used, and if budget allows, RAID1 offers the most stability and reliability.