A brief introduction of the advantages and disadvantages of RAID model:
1: The advantages and disadvantages of RAID model, which is widely used at present, are as follows:
1. RAID 0 mode
Advantages: In RAID 0, the storage data is divided into two parts and stored on two hard disks respectively. At this time, the theoretical storage speed of mobile hard disks is twice as fast as that of a single hard disk, and the actual capacity is twice as large as that of a smaller hard disk in two hard disks.
Disadvantage: If any hard disk fails, the data on the entire RAID will not be recoverable.
Note: Storing HD movies is more suitable.
2. RAID 1 Model
Advantages: In this mode, two hard disks mirror each other. When a hard disk is damaged, replacing the original hard disk with a new hard disk (greater than or equal to the original capacity) can automatically restore data and continue to use. The actual capacity of the mobile hard disk is equal to the capacity of a smaller hard disk, and the storage speed is the same as that of a single hard disk. The advantage of RAID 1 is that if any hard disk fails, the stored data will not be lost.
Disadvantage: The actual capacity of the hard disk used in this mode is relatively small, only the smallest capacity of the two hard disks.
Note: Important information, such as databases and personal data, is a safe storage scheme.
3. RAID 0+1 mode
RAID 0+1 is a combination of disk segmentation and mirroring. Two RAID 0 arrays are mirrored each other, and then they become an array of RAID 1. Hard disk usage is only 50%, but provides the best speed and reliability.
4. RAID 5 mode
Rather than backing up the stored data, RAID 5 stores the data and corresponding parity information on the disks that make up RAID 5, and the parity information and corresponding data are stored on different disks respectively. When a disk data of RAID 5 is damaged, the damaged data is recovered by using the remaining data and the corresponding parity information. If you want to raid 5 data recovery, You must select a data recovery software for it.
5. RAID 10 mode
RAID 10 requires at least four hard disks to complete. Two hard disks are made up of one RAID 1, and then two groups of RAID 1 are made up of one RAID 0. Although RAID 10 causes 50% disk waste, it provides 200% speed and data security with single disk damage.
2: Final RAID Model:
1, concept
RAID (Redundant Arrays of Inexpensive Disks) means "cheap and redundant disk arrays". The principle is to use the array method as the disk group, cooperate with the design of data scattered arrangement, improve the security of data. Disk array is composed of many inexpensive, small capacity, high stability and slow speed disks, which are combined into a large disk group. The effect of using individual disks to provide data improves the efficiency of the whole disk system. At the same time, using this technology, the data are cut into many sections and stored on each hard disk separately. Disk arrays can also use the concept of Parity Check to read data when any hard disk in the array fails, and re-place the data into the new hard disk after calculation when data is reconstructed.
2, specification
RAID technology mainly includes several specifications, such as RAID 0-RAID 50, with different emphasis. There are several common specifications as follows:
RAID 0: RAID 0 divides data in bits or bytes continuously and reads/writes it on multiple disks in parallel, so it has a high data transmission rate, but it has no data redundancy, so it can not be regarded as a real RAID structure. RAID 0 simply improves performance without guaranteeing data reliability, and one disk failure affects all data. Therefore, RAID 0 can not be applied to high data security requirements.
RAID 1: It realizes data redundancy through disk data mirroring and generates backup data on paired independent disks. When the original data is busy, it can read directly from the mirror copy, so RAID 1 can improve the reading performance. RAID 1 is the most expensive unit in disk array, but it provides high data security and availability. When a disk fails, the system can automatically switch to a mirror disk to read and write without reorganizing the failed data.
RAID 0+1: Also known as RAID 10 standard, it is actually the product of combining RAID 0 and RAID 1 standard. It divides data in bits or bytes continuously and reads/writes multiple disks in parallel, at the same time, it makes disk image redundant for each disk. Its advantage is that it has both the extraordinary speed of RAID 0 and the high reliability of RAID 1 data, but the CPU occupancy is also higher, and disk utilization is relatively low.
RAID 5: RAID 5 does not specify parity disks separately, but cross-accesses data and parity information on all disks. On RAID 5, read/write pointers can operate array devices simultaneously, providing higher data traffic. RAID 5 is more suitable for small data blocks and random read-write data. Compared with RAID 5, the main difference between RAID 3 and RAID 5 is that every time RAID 3 transmits data, it involves all the array disks; for RAID 5, most data transfers only operate on one disk and can be operated in parallel. There is "write loss" in RAID 5, that is, each write operation will produce four actual read/write operations, of which two read old data and parity information, and two write new data and parity information.
3, advantages
Increase the transmission rate. RAID greatly improves the data throughput of storage system by storing and reading data on multiple disks at the same time. In RAID, many disk drives can transmit data at the same time, and these disk drives are logically a disk drive, so using RAID can achieve several times, tens or even hundreds of times the speed of a single disk drive. This is also the problem RAID initially wanted to solve. Because the speed of CPU increased rapidly at that time, and the data transmission rate of disk drives could not be greatly improved, so a solution was needed to solve the contradiction between the two. RAID finally succeeded.
Fault tolerance is provided through data validation. Ordinary disk drives cannot provide fault tolerance if they do not include C R C codes written on disk. RAID fault tolerance is built on the hardware fault tolerance function of each disk drive, so it provides higher security. In many RAID modes, there are more complete measures of mutual check/recovery, even direct mutual mirror backup, which greatly improves the fault tolerance of RAID system and the stability and redundancy of the system.
4, implementation
Disk arrays can be implemented in two ways: software arrays and hardware arrays.
Software array refers to the configuration of multiple hard disks on the connected SCSI card into logical disks through the disk management function provided by the network operating system itself to form an array. Software arrays can provide data redundancy, but the performance of disk subsystems will be reduced, some of which are still relatively large, up to about 30
Hardware arrays are implemented using special disk array cards. Hardware arrays can provide on-line expansion, dynamic modification of array level, automatic data recovery, driver roaming, ultra-high-speed buffer and other functions. It provides solutions for performance, data protection, reliability, availability and manageability. The performance of the special processing unit of the array card is much higher than that of the conventional non-array hard disk, and it is safer and more stable.
In fact, disk arrays are also divided into two kinds: Software Raid and Hardware Raid. Soft arrays are made up of software programs and CPU of computer. Because software programs are not a complete system, they can only provide the most basic RAID fault-tolerant functions. Others, such as hot standby hard disk settings, remote management and other functions, are all underappreciated. Hard arrays are independent. The operating hardware provides the control and calculation functions of the whole disk array, and does not depend on the CPU resources of the system.
Hard arrays are a complete system and all required functions can be done. So the functions and performance provided by hard arrays are better than that of soft arrays. Moreover, if you want to make the system into disk arrays, hard arrays are the only choice. So we can see that the RAID level 5 disk arrays on the market are all hard arrays. Soft arrays are only suitable for Raid 0 and Raid 1. For me, the RAID level 5 disk arrays are hard arrays. They will definitely not use Raid 0 or Raid 1 as mirror towers. As a high-performance storage system, it has been more and more widely used. The level of RAID has developed six levels from the concept of RAID to now, which are 0, 1, 2, 3, 4, 5 and so on. But the most commonly used level is 0, 1, 3, 5.