The RAID system is an effective means to protect data from stored data. In the RAID creation process, there is often a very long time system initialization process. Why is there such an operation in the RAID initialization process? What aspects will this operation have on SSD? Let's analyze and study the RAID initialization process from the perspective of technology development.   The basic organizational structure of a traditional RAID array is that all disks added to a RAID Group are divided into a series of slices based on their LBA addresses. These slices are called Stripe Units. Stripe units corresponding to the same LBA addresses on different disks are organized into a Stripe. Encoding all data in one strip, such as RAID6 producing two encoded data blocks P and Q, allows both data disks to be corrupted at the same time.   Therefore, in the RAID system, all the data in the strip need to meet the rules of coding and dec algorithm, that is, all the data in the strip can generate coding data according to certain rules, and the coding data is the same as the coding data stored in the strip. This situation is called the data in that band. When a disk fails, the lost data blocks can be recovered by the encoded data stored in the strip.   If the data in a strip is inconsistent, that is, the coding result obtained by the data in the strip is not the same, then once a disk fails, the missing data block cannot be properly recovered by the coded data stored in the strip. Therefore, a strip of data inconsistency that will cause data correctness issues when the fault occurs. When creating a RAID system, the disk in the RAID Group may be either a new disk or a data disk that has already been used, where all data will not be zero. In this case, the data strips constructed with these disks must not meet the need of data consistency. That is, the coding data in each band calculated according to certain rules is inconsistent with the coding data in the band. Such data-inconsistent bands will introduce a great risk to the problem of RAID data correctness.   For this reason, when creating a RAID, you need to consider initializing all the strips in the system to ensure the consistency of the data in the bands. Band initialization can usually be solved in two ways: 1. Initializes all the bands in the RAID system by writing the total zero. All data zero band, its check data is also zero. Therefore, all-zero data can guarantee band consistency. 2. Check all the strips and update the check data in the strips to achieve the consistency of the strip data.   When a RAID system is initialized, the data in all bands will become consistent.The RAID system initialization process is a very long process, mainly because the need to initialize all the bands in the system. The performance balance between the front-end user IO, so RAID system initialization is often a background execution process, which will last for a long time and affect the performance of front-end applications.   For SSDS, the RAID system initialization process also introduces other problems. During system initialization, data needs to be written to SSDS, no matter in zero write or parity data update mode. This process results in unnecessary data write enlargement. Before user data is written, a data mapping table is established inside the SSD through initialization. The service life and performance of SSDS are reduced. Therefore, a RAID system for SSDS needs to be optimized for the system initialization process, which is a special feature that traditional RAID does not take into account. Therefore, traditional RAID arrays cannot be directly deployed on SSDS, which affects SSD service life and performance.   RAID systems use striping to protect data, but a series of problems are also introduced in the process of striping data protection. System initialization is a typical problem of strip consistency. A good RAID Data protection system will solve this problem during the design process. For example, EMC Data Domain RAID does not have the system initialization process, of course, it needs to cooperate with the file system, and has done a lot of optimization in RAID strip data distribution.