Shulou(Shulou.com)06/01 Report--

1. RAID disk array

RAID is the abbreviation of Redundant Array of Independent Disks in English and independent redundant disk array in Chinese. To put it simply, RAID is a combination of multiple independent hard drives (physical hard drives) in different ways to form a hard disk group (logical hard disk), thus providing higher storage performance and data backup technology than a single hard disk. The different ways of forming a disk array are called RAID levels (RAID Levels). To the user, the disk group is like a hard disk, which can be partitioned, formatted, and so on. In short, the operation of a disk array is exactly the same as that of a single hard disk. The difference is that disk arrays store much faster than individual hard drives and provide automatic data backup. The function of data backup is that once the user data is damaged, the damaged data can be recovered by using the backup information, thus ensuring the security of the user data.

Second, the two characteristics of RAID technology.

One is speed, the other is security. Because of these two advantages, RAID technology was early used in the hard disk system with SCSI interface in advanced servers. With the development of computer technology in recent years, the speed of PC CPU has entered the GHz era. The hard disk of IDE interface is not to be lagged behind, and ATA66 and ATA100 hard drives have been launched one after another. This makes it possible for RAID technology to be applied to low-and middle-grade or even personal PCs. RAID is usually implemented by a RAID controller in a hard disk array tower or a raid card in a computer.

Third, the implementation of mirror redundancy.

4. XOR algorithm

The same is true and the different is false.

V. RAID level

The different ways to form a RAID array are called RAID levels

Different RAID levels have different effects:

Different storage performanc

Different data reliability

Different storage costs

The mainstream can be divided into several levels: RAID 0meme raid 1m raid 3m raid 5m raid 10m raid 50.

1 、 RAID0

The data is distributed evenly on each disk of the array in the form of stripes. RAID 0 continuously divides the data in bits or bytes and reads / writes in parallel on multiple disks, so it has a high data transfer rate, but it has no data redundancy, so it can not be regarded as a real RAID structure. RAID 0 simply improves performance and does not guarantee the reliability of the data, and the failure of one of the disks will affect all data. Therefore, RAID 0 can not be used in situations with high data security requirements.

2 、 RAID1

It realizes data redundancy through disk data mirroring and produces data backed up by each other on pairs of independent disks. When the original data is busy, the data can be read directly from the mirrored copy, so RAID 1 can improve read performance. RAID 1 has the highest unit cost of the disk array, but provides high data security and availability. When a disk fails, the system can automatically switch to the mirrored disk to read and write without the need to reorganize the failed data.

3. RAID 10 (Note: 10 is not the number 10, here it means 10,)

In fact, it is the product of the combination of RAID 1 and RAID 0 standard, which stripes each disk as a disk mirror while continuously dividing data in bits or bytes and reading / writing multiple disks in parallel. Its advantage is that it has both the extraordinary speed of RAID 0 and the high data reliability of RAID 1, but the CPU occupancy is also higher, and the disk utilization is relatively low.

4 、 RAID 2

The data is distributed on different hard drives in bits or bytes, and a coding technique called "weighted average error correction code (hamming code)" is used to provide error checking and recovery. This coding technique requires multiple disks to store inspection and recover information, which makes the implementation of RAID 2 technology more complex, so it is rarely used in business environments.

5 、 RAID 3

It is very similar to RAID 2 in that it strips data across different hard drives, except that RAID 3 uses simple parity and uses a single disk to store parity information. If a disk fails, the parity disk and other data disks can regenerate the data; if the parity disk fails, the data usage will not be affected. RAID 3 can provide a good transfer rate for a large amount of continuous data, but for random data, parity disks can become the bottleneck of write operations.

6 、 RAID 5

RAID 5 does not specify a separate parity disk, but accesses data and parity information across all disks. On RAID 5, read / write pointers operate on array devices at the same time, providing higher data traffic. RAID 5 is more suitable for small data blocks and random read-write data.

7 、 RAID50

It is a combination of RAID5 and RAID0. This configuration strips data, including parity information, on each disk of the subdisk group of the RAID5. Three hard drives are required for each RAID5 subdisk group. RAID50 is more fault tolerant because it allows one disk in a group to fail without data loss. And because the parity bit is partial on the raid 5 subdisk group, the reconstruction speed is greatly improved. Advantages: higher fault tolerance and the potential for faster data reading rates. It is important to note that disk failures can affect throughput. It takes longer to rebuild information after a failure than in the case of a mirror configuration.

VI. Comparison of commonly used RAID levels

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.