Raid Disk Array Technology

Aid Definition
RAID (Redundant Array of independent disk independent redundant disk array) technology is the University of California, Berkeley, 1987
It was initially proposed to combine small and low-cost disks to replace large and expensive disks. At the same time, it was hoped that access to data would not be damaged when the disk fails.
Develop a certain level of data protection technology. Raid is a Redundant Array composed of multiple low-cost disks.
Is an independent large storage device. Raid can give full play to the advantages of multiple hard disks, increase the speed and capacity of hard disks,
The Fault Tolerance function is provided to ensure data security and ease of management. You can continue to work if any hard disk is faulty,
The disk will not be damaged.
Ii. Several raid Modes
1. raid0
That is, data stripping data sharding technology. RAID 0 can connect multiple hard disks into a larger hard disk group, which can improve the disk
Disk performance and throughput. RAID 0 has no redundancy or error repair capability, and the cost is low. It requires at least two disks, usually only in the logarithm
It is used only when the security requirements are not high.
(1) RAID 0 is the easiest way
It means to use X hard disks in the form of hardware through the smart disk controller or the disk driver in the operating system
Form an independent logical drive, which is X times the capacity of a separate hard disk and is written to each disk in sequence when writing computer data.
When the space of a disk is exhausted, data is automatically written to the next disk. The advantage is that the disk capacity can be increased.
The speed is the same as that of any disk. If any disk fails, the entire system will be damaged and reliable.
Is to use a hard disk separately 1/N.
(2) Another RAID 0 Method
Create a zone set using N hard disks with a reasonable size. It is best to assign a dedicated disk controller to each hard disk.
When reading and writing computer data to N disks at the same time, the speed is increased by N times. Improve system performance.
2. Raid 1
Raid 1 is called a disk image: It mirrors data from one disk to another, ensuring maximum performance without affecting the performance.
The system has high data redundancy capability in terms of reliability and maintainability, but the disk utilization is 50%, so the cost is the highest and is mostly stored.
Important data. Raid 1 has the following features:
(1) Each disk in Raid 1 has a corresponding image disk, and data is synchronized to the image at any time. The system can
Read data from any disk on the image disk.
(2) the space used by the disk is only half of the total disk capacity, and the system cost is high.
(3) As long as there is at least one disk in any one of the system's image disks, you can even ask questions in the case of half of the number of hard disks.
The system can run normally.
(4) If the RAID system is no longer reliable due to a hard disk failure, the damaged hard disk should be replaced in time; otherwise, the remaining image disks will also appear.
The system crashes.
(5) After the new disk is changed, the original data will need a long time synchronization Image, and external access to the data will not be affected.
The performance of the entire system has declined.
(6) RAID 1 has a large disk controller load. Using Multiple disk controllers can improve data security and availability.
3. raid0 + 1
Combined with raid0 and raid1 technologies, each disk has its physical image disk, which provides full redundancy.
Force, allows one or more disk failures without affecting data availability, and has the ability to read/write quickly. Raid0 + 1 to be created in the disk image
There must be at least four hard disks in the band.
4. raid2
When writing data, the computer saves the bit of data on a disk, and calculates the Hamming checkcode for each bit of data.
Save another set of disks, because the Hamming code can correct errors in case of data errors, to ensure that the output is correct. But Hamming Code
With data redundancy technology, the speed of output data depends on the slowest disk in the drive group. The raid2 controller is easy to design.
5. raid3: parallel transmission with parity Codes
RAID 3 uses a dedicated disk to store all the verification data, and creates read/write operations with Scattered Data in the remaining disk
. When reading data from an intact RAID 3 system, you only need to find the corresponding data block in the data storage disk for read operations. However
When writing data to raid 3, you must calculate the check value of all data blocks in the same zone as the data block and re-write the new value
Check block, which increases the system overhead. When a disk fails, all data blocks on the disk must be verified again.
Create. If the data block to be read is located in the damaged disk, you must read all other data blocks in the same zone at the same time,
The loss of data is re-built based on the check value, which slows down the system. After a damaged disk is replaced, the system must have one data block and one data block.
The data in the bad disk is rebuilt, and the performance of the entire system will be seriously affected. The biggest disadvantage of RAID 3 is that the verification disk can easily become the entire system.
For applications with frequent write operations, the performance of the entire raid system may decline. RAID 3 is suitable for databases and web servers.
Server.
6. raid4
Raid4 is an independent disk structure with a parity code. raid4 and raid3 are very similar. It accesses data by data block and
It is carried out by disk. Each time it is a disk, raid4 features exactly the same as raid3, but it is more difficult than raid4.
Raid3 is much larger, the controller design is much more difficult, and the data access efficiency is not very good.
7. RAID5
RAID 5 disperses the verification block to all data disks. RAID 5 uses a special algorithm to calculate any zone-based school.
The storage location of the block. This ensures that any read/write operations on the verification block are balanced across all RAID disks.
Eliminate the possibility of bottlenecks. The reading efficiency of RAID5 is very high, the writing efficiency is average, and the block-based collective access efficiency is good. RAID 5 Improvement
System reliability, but it does not solve the data transmission concurrency well, and the controller design is also quite difficult.
8. raid6
Raid6 is an independent disk structure with two parity codes for distributed storage. It is an extension of RAID5 and is mainly used to request data.
When two parity values are used, N + two disks are required, and the design of the controller becomes very complex.
The write speed is not good. It takes a lot of time to calculate the parity value and verify the data correctness, resulting in unnecessary load,
Rarely used.
9. raid7
Raid7 is the optimized high-speed data transmission disk structure. All its I/O transmissions are synchronized and can be controlled separately, which improves
The system concurrency and the speed at which the system accesses data. Each disk has a high-speed buffer storage, and the real-time operating system can use any
Operating chip to meet the needs of different real-time systems. Allows you to use the SNMP protocol for management and monitoring. You can specify an independent transfer in the verification area.
To improve efficiency. Multiple hosts can be connected. When multiple users access the system, the access time is close to 0. However, if the system loses power
The data in the high-speed buffer memory will be completely lost, so it is necessary to work with the ups, raid7 system cost is very high.
10. raid10
Raid10 is a high-reliability and efficient disk structure. It is a band structure and a mirror structure, which can achieve both high efficiency and high speed. This
The new structure has a high price and poor scalability.
11. raid53
Raid7 refers to the efficient data transmission disk structure, which is the unified structure of raid3 and band. Therefore, it is fast and fault-tolerant. But the price
Very high, not easy to implement.
Iii. Application of RAID technology
There are two main ways to use disk raid. The first is raid adapter, which is used to insert a PCI slot into the raid adapter and connect the hard disk.
Implement the raid function of the hard disk. The second method is to directly integrate the raid control chip on the motherboard so that the motherboard can directly implement disk raid. This
The cost is much lower than the dedicated raid adapter.
In addition, you can use a 2 K or XP or Linux system to create a soft RAID.
Raid is usually used in RAID 0, RAID 1, or RAID 0 + 1 mode.
4. Using HP xw4200 workstation as an example to describe how to configure raid for Enterprises)
Product Information
HP xw4200 workstation uses Intel 925x express North Bridge + ich6r South Bridge.
Software required
When configuring raid, you must first install the software, that is, the independent RAID card driver. The method for downloading the software is as follows:
Open HP Chinese site home http://www.hp.com.cn /;
Click "support and driver ";