RAID Redundant Array of Disks
RAID technology combines multiple hard disk devices into one capacity A larger and more secure disk array, and the data is divided into multiple segments and stored on different physical hard disk devices. Then, the distributed read and write technology is used to improve the overall performance of the disk array, and multiple Copies of important data are synchronized to different physical hard disk devices, thus playing a very good data redundancy backup effect.
Everything has its two sides. RAID technology does have a very good data redundancy backup function, but it also increases costs accordingly. Just as we only had one phone book originally, but in order to avoid loss, we wrote the contact number information in two copies. Naturally, we have to buy an extra phone book for this, which will increase the cost accordingly. The original intention of RAID technology is to reduce the cost of purchasing hard disk equipment, but compared with the value of the data itself, modern enterprises value the redundant backup mechanism of RAID technology and the increase in hard disk throughput. promote. In other words, RAID not only reduces the probability of data loss after the hard disk device is damaged, but also improves the read and write speed of the hard disk device. Therefore, it is widely deployed and applied in most operators or large and medium-sized enterprises.
Due to cost and technical considerations, it is necessary to make trade-offs between data reliability and read and write performance for different needs, and develop different solutions to meet their respective needs. There are currently at least a dozen RAID disk array schemes, and Mr. Liu Dun will explain in detail the 4 most common schemes of RAID 0, RAID 1, RAID 5 and RAID 10
RAID 0
The RAID 0 technology connects multiple physical hard disk devices (at least two) through hardware or software to form one Large volume group, and write data to each physical hard disk in turn. In this way, in the most ideal state, the read and write performance of the hard disk device will increase several times, but if any one hard disk fails, the data of the entire system will be destroyed. Generally speaking, RAID 0 technology can effectively increase the throughput of hard disk data, but it does not have the ability to back up data and repair errors.
RAID 1
RAID 1 technology is to bind two or more hard disk devices. When data is written, the data is written to On multiple hard disk devices (it can be regarded as a mirror image or backup of data). When one of the hard disks fails, the normal use of data will generally be restored immediately by hot swapping.
RAID 5
RAID5 technology is to save the data parity information of the hard disk device to other hard disk devices. The parity information of the data in the RAID 5 disk array group is not stored separately in a certain hard disk device, but stored on every other hard disk device except itself. The advantage of this is that any one of the devices will not be damaged after damage. There is a fatal flaw; the parity part of the figure stores the parity information of the data. In other words, the RAID 5 technology does not actually back up the real data information in the hard disk, but passes the parity information when the hard disk device has a problem. To try to reconstruct the damaged data. Technical features such as RAID “compromise” to take into account the read and write speed of hard disk devices, data security and storage costs.
RAID 10
RAID 10 technology is a “combination” of RAID 1+RAID 0 technology. As shown in Figure 7-4, the RAID 10 technology requires at least 4 hard disks to build. First, make a RAID 1 disk array in pairs to ensure data security; then implement RAID 0 on the two RAID 1 disk arrays. Technology to further improve the read and write speed of hard disk devices. In this way, theoretically speaking, as long as not all the hard disks in the same group are damaged, up to 50% of the hard disk devices can be damaged without losing data. Because RAID 10 technology inherits the high read and write speed of RAID 0 and the data security of RAID 1, the performance of RAID 10 surpasses RAID 5 regardless of cost, so it is currently a widely used storage technology.
Deploy Disk Array
mdadm command is used to manage software RAID hard disk array in Linux system, the format is “mdadm [mode]
Common parameters and functions of the mdadm command
Parameter Function
-a Detection device name
-n Specifies the number of devices
-l specify RAID level
-C created
-v display process
-f simulation equipment damage
-r remove a device
-Q view summary information
-D View detailed information
-S Stop RAID disk array
