Basic Introduction to raid

I. Disadvantages of traditional disks

The components that affect computer performance typically include: CPU, motherboard bus io, memory io, hard disk io, Nic io. Modern processor performance is already high, but the overall IO performance of the computer is weak, which seriously affects the computer performance.

Modern computer bus, memory speed can reach 5G per second, or even higher, but hard disk IO is often low:

Drive type Speed

SATA <150m/s

SCSI <200m/s

SAS 200m/s Around

SSD 500m/s Around

Hard drives are a performance bottleneck for most computers

two. RAID

1. Modern hard disk Flaw: IO performance is very weak, the stability is very poor

2.RAID (Redundant array of independent Disks) low-cost HDD Redundant array technology improves the storage IO performance of your computer by running multiple disks in parallel.

3.RAID is divided into many categories, called RAID level, modern raid a total of 7 classes, commonly used in the following four categories:

-raid 0 Read and write performance

-raid 1 Read and write performance, redundancy

-raid 5 Read and write performance, redundancy (one hard drive)

-raid 6 Read and write performance, redundancy (two HDD)

three. RAID 0

RAID0 uses a minimum of 2 hard drives to read and write data separately and read and write to multiple hard drives to improve read and write performance.

Space utilization: The sum of all hard disk space

Performance: The sum of all hard drive speeds

Redundancy capability: None

four. RAID 1

RAID 1 uses a minimum of 2 hard drives to copy and write data to multiple hard drives when writing data. To improve redundancy when reading data. Read data from multiple hard drives at the same time to improve read performance.

Space utilization: The smallest piece of all disks

Performance: Read performance is the sum of all disk speeds, write performance will be reduced

Redundancy: As long as a hard drive is normal, the data is normal

Five. RAID 5

RAID 5 uses a minimum of 3 hard drives, RAID5 and RAID0 similar, read and write data when the data will be distributed read and write on all the hard disk, but in the writing of data will be the data parity operation, officer inspection information at the same time saved on the hard disk, verification information can be used for data recovery.

Space utilization: 1-1/n

Performance: Read performance close to RAID0, write performance is weaker than RAID0

Redundant capacity: 1 hard drive damage is acceptable

Six. RAID 6

RAID 6 uses a minimum of 4 hard drives, RAID6 and RAID5 similar, read and write data will be distributed to read and write data on all the hard disk, and save parity information, but will be more than RAID5 to save a checksum, so redundancy more RAID5 increased.

Space utilization: 1-2/n

Performance: Read and write performance close to RAID5, reading performance is weaker than RAID5

Redundant capacity: 2 hard drive damage is acceptable

seven. RAID implementations

There are two ways to implement RAID:

1. Software raid

RAID with system functions or RAID software, without independent hardware and interfaces, requires a certain amount of system resources (CPU, hard disk interface speed) and is affected by operating system stability.

2. Hardware RAID

With a separate RAID hardware card, some motherboards integrate RAID hardware, some need to purchase a separate RAID hardware card, hardware RAID implementations do not need to occupy other hardware resources, stability and speed are stronger than software raid

Basic Introduction to raid