RAID disk array

I. Introduction to RAID Disk Array

The full name of the disk array (Redundant Arrays of Inexpensive Disk, RAID), the Chinese abbreviation is Independent Redundant Disk Array.RAID can integrate multiple independent physical hard disks into a larger hard disk group (logical hard disk) through technology (software or hardware), which can be partitioned and formatted by users. In addition to storage, this logical hard disk also hasThe function of data protection provides data backup technology. RAID technology is divided into several different levels, which can provide different speed, security and cost performance.Selecting an appropriate RAID level according to the actual situation can meet the user's requirements for the availability, performance and capacity of the storage system. Due to the different levels selected for the entire RAID, the read and write performance of the integrated hard disks is somewhat different. The commonly used levels are:The following commonly used RAID levels are as follows: RAID0, RAID1, RAID5, RAID1+0, etc.

Second, RAID 0

Because both reads and writes can be processed in parallel, RAID 0 is the fastest of all levels.But RAID 0 is neither redundant nor fault tolerant, if one disk is (physically) damaged, all data is lost.

Read and write performance improvement free space: N*min(S1,S2,...)

No fault tolerance

Minimum number of disks: 1+

Three, RAID 1

Also called mirroring, more than two groups of N disks mirror each other, which can have a very good read speed in some multi-threaded operating systems. Theoretically, the read speed is equal to the multiple of the number of hard disks, which is the same as RAID 0..In addition, there is a slight decrease in the writing speed.

Improved read performance and slightly decreased write performance

Available space: 1*min(S1,S2,...)

Disk utilization 50%

Redundant ability

Minimum number of disks: 2n

Three, RAID 5

Improved read and write performance

Available space: (N-1)*min(S1,S2,...)

Fault-tolerant: allow up to 1 disk corruption

Minimum number of disks: 3, 3+

Four. RAID 1+0

N (even, N>=4) disks are mirrored in pairs, and then combined into a RAID 0;

N/2 disk utilization, low usage;

N/2 disks are written at the same time, and N disks are read at the same time;

High performance, high reliability

V. Array card

1. An array card is a board used to implement RAID functions, usually composed of a series of components such as I/O processors, hard disk controllers, hard disk connectors and caches

2. Different RAID cards support different RAID functions: such as RAID0, RAID1, RAID5, RAID10, etc.

3. Interface type of RAID card:

• IDE interface (parallel interface, low price, strong compatibility)
• SCSI interface (serial interface, is a small computer system interface, widely used in high-speed data transmission technology on small computers, supports hot swap, low CPU usage, but high price)
• SATA interface (serial interface)
• SAS interface (a new generation of scsi interface, backward compatible with SATA)