You will be able to understand this! Use a water dispenser to teach you what raid is

ArticleDirectory

• Question 1: What is raid? What is it composed?
• Question 2: When do I need raid?

If you have time, blow more water. RAID technology can be used to blow a few barrels of water.

You will be able to understand this! Use a water dispenser to teach you what raid is

Question 1: What is raid? What is it composed?

Raid is a Redundant Array of disks. As its name suggests, raid is an array composed of disks. Therefore, raid requires at least two hard disks. The basic idea of raid is to combine multiple cheap small disks into one disk group, so that the performance can reach or exceed a large and expensive disk.

The original intention of raid was not to improve data security, but to speed up the reading and writing of hard disks. RAID 0 and RAID 1 are defined for this purpose.

Question 2: When do I need raid?

Depending on the actual situation, we should adopt different raid types for servers as network administrators. Currently, RAID 0, RAID 1, and RAID 5 are the most popular. Among them, raid1 and RAID 5 are used to ensure data security and prevent data loss due to unexpected disk damage to the maximum extent. RAID 0 aims to speed up disk reading and does not provide any data backup and protection functions. We can select different raid applications based on the actual situation.

Of course, it is very convenient for those who need to store a large amount of data on the hard disk to use RAID technology. Mainly manifested in the following aspects --

(1) enhanced speed. The server can read data from multiple hard disks at the same time.

(2) the storage capacity is expanded, and multiple hard disks constitute a larger space for the server to use.

(3) The disk can be efficiently restored. Raid provides a high level of data redundancy, which ensures data integrity.

Question 3: What types of RAID are available? We hope you can use a language that is intuitive and easy to understand.

I am afraid many articles have introduced raid types. I will not elaborate on the theory here. I have seen an image describing RAID levels in foreign countries. I feel that the definition of raid is very accurate in many places, and the raid effect is more remarkable by looking at the picture. (1)

 

 

(1) Let's explain the first small chart, that is, the water dispenser marked with standalone. This figure mainly compares the differences between raid types by providing water sources for water dispensers through mineral water buckets. The water outlet holes of the two water dispensers are equivalent to the interface for reading data, while the water in the water bucket is valuable data. The data is read by the user through the data interface of the water hole. A mineral water corresponds to a hard disk.

Under normal circumstances, our computer (such as a home computer rather than a server) has only one hard disk. At this time, we need to drink water (read hard disk data) and water sources are provided by this mineral water bucket. (2)

 

(2) Next, let's look at the second small graph, that is, the graph marked with the cluster. (3) The so-called cluster is the meaning of the cluster, the cluster is to combine multiple servers into one, all servers provide the same service and data. As shown in the figure, there are two water dispensers, indicating two servers. Both servers can provide user data (water source ).

Users can obtain data from the water dispenser on the left or from the water dispenser on the right, which virtually provides the efficiency for users to obtain water (data. However, this cluster has one disadvantage: hardware support from multiple servers is required, which is a waste to some extent. Generally, small and medium-sized enterprises cannot allow multiple servers to provide the same data and services.

 

(3) The third small icon remembers Hot Swap. (4) It means hot exchange. It is similar in concept to hot backup. That is, a water dispenser (server), like the first figure, has a hard disk and the same amount of water as standalone. However, when the water tank on the water dispenser is faulty, for example, the water is lost or the bucket is broken, heat exchange technology is adopted immediately to replace the faulty bucket with the water tank on the water dispenser, to continue providing services. However, this method also has a disadvantage, that is, a bucket is required for backup and can be used only when the original bucket has a problem. In addition, the bucket change process takes time, which virtually affects the provision of services.

 

(4) Figure 4 shows the raid leader. Here he is the leader because he is the first raid. Level 0 is raid level 0, which is usually called a zone. It is a specific performance using the zone data ing technique. That is to say, when data is written to the disk group, the data is divided into zones and is staggered into the disk of the disk group. This brings high I/O performance and low overhead, but does not provide any redundancy. The storage capacity of the disk group is equal to the sum of the total disk capacity. (5)

When either of the two buckets on the water dispenser fails, the user cannot obtain valuable data (Water Source) through the water outlet. Therefore, the user does not provide redundancy. Of course, in the process of obtaining the water source, the user obtains it through two mineral water buckets at the same time. Naturally, it has an advantage over using only one bucket in many aspects such as water output. Improving data read/write speed is the biggest feature of RAID 0.

Some readers may ask if the top bucket in RAID 0 has a problem. Isn't it the same? In fact, this figure is just to help you remember and understand raid. It is impossible to use a simple figure to reflect the raid types that can be clearly stated only by theoretical description. Therefore, you should not be too rigid in understanding images.

(5) The fifth figure is also commonly used in raid. Level 1 is raid Level 1, which is often referred to as image raid. (6) compared with other RAID levels, this level takes a long time. Raid 1 provides data redundancy by writing the same data to each disk of the disk group and copying the "image" to each disk. Images are very popular because of their simple implementation and high data reliability.

When reading data at level 1, two or more disks are processed in parallel. Therefore, the data transmission rate is high, but other operations cannot provide high-speed I/O transmission rates. Level 1 provides excellent data reliability and improves the performance of read data operations, but it is very expensive. The disk types of the disk must be the same, and the size of the disk after the disk is composed must be equal to the size of one disk.

As shown in the middle, there are two mineral water buckets placed on the water dispenser, so that when one of them has a problem, such as damage or no water, it will not affect the use of mineral water, because another bucket will provide water in good condition. Of course, because the water outlet has not been expanded, the water output is the same as that of a mineral water bucket. Therefore, although the output speed remains unchanged, an additional bucket makes RAID 1 provide maximum redundancy, but it cannot improve the reading speed.

TIPS:

There is a detail that requires special attention from readers. In the Raid 1 picture, two mineral water buckets share one water supply port, and the natural water output remains unchanged. The RAID 5 below is different. I will explain it in detail later.

(6) The sixth figure shows the most common raid level for servers, namely RAID 5. (7) The servers purchased by my company, Whether Dell or IBM or sugon server, use this most common raid type. This level of raid is to distribute parity to some or all disks in the disk group, and the Level 5 usually uses the buffer technology to reduce the performance asymmetry. If the disk types of a disk are the same, the disk capacity equals the total capacity of the disk, minus the capacity of a disk.

As mentioned above, RAID 1 only uses a water supply port and does not increase the water output speed. However, in RAID 5, we will find that the three mineral water buckets in Figure 7 are installed in three water portals, so that we can provide water sources for users at the same time, naturally, the effluent speed has been greatly improved. It does not matter if one of the three mineral water buckets has problems, which will not affect the drinking water source.

TIPS:

There are two points that are not shown in the figure. Here we will illustrate how to help readers have a clear understanding. (1) Figure 7 shows only three buckets. In reality, RAID5 can be configured as long as we have more than three hard disks (buckets. Four, five or more hard disks to configure RAID 5 are no problem. (2) If two or more hard disks are faulty after RAID 5 is configured, data cannot be effectively protected. That is to say, RAID 5 can only ensure data integrity when one of the hard disks fails.

(7) The last figure is actually a combination of RAID 0 and RAID 1, as long as you have a clear understanding of RAID 0 and RAID 1, this figure is much simpler to understand. In fact, it is configured as RAID 0 first, and then RAID 1 is configured. It plays all the advantages of RAID 0 and 1 accordingly, all of their shortcomings are avoided. In view of the length of the article, we will not detail it here. After all, RAID 0 + 1 has no chance of using RAID 5 in actual work.

Summary:

For readers who are not very familiar with servers, mastering raid is the most basic concept. He is a stepping stone in our field of server knowledge. I hope the water dispenser diagram in this article will help you understand various RAID and data redundancy categories. Finally, I would like to reiterate that it is only for the convenience of understanding and remembering. Many details and features of RAID theory cannot be expressed through simple images, if the image description is incomplete, please forgive me. After all, this article is intended for readers of RAID knowledge.