Definition
Data block is a group of records arranged in sequence, between the main memory and the input, output device or external memory A unit of data for transmission. It is the physical record of data, and the corresponding relationship between the logical record of data (logically related, and the data unit of a group of adjacent units on the memory) has three ways: ①a block is a record; ②a block Contains several logical records; ③One logical record occupies several blocks. The size of the data block can be fixed or variable, and there are gaps between blocks. The design data block size is affected by many factors, including input and output efficiency, storage space cost, and computer application characteristics.
The main memory and the cache are divided into data blocks of equal length. Each time the main memory and the cache exchange data, the data block is used as the unit.
In SQL Server:
In text, ntext, and image data, the data block is the data that is transferred once between the application and the SQL Server instance Unit. The term also applies to storage units of these data types. In the tape backup file, the data block is the unit of physical I/O.
Data block in the Flash chip
The concept of the data block in the Flash chip is a logical concept, and is different from the physical parameters referred to by the chip. It means that the data ID number is the same and Consisting of adjacent pages in physical location. That is to say, the data ID numbers of all pages in a block are the same, and the positions of these pages in the chip are adjacent. Therefore, the number of pages composing each block may be different, or it is possible that one page composes one block, and multiple pages compose one block.
The concept of the data block of the Flash chip is an abstract concept. It must have the following characteristics:
1. The ID number is the same, that is, all pages in the same data block The ID numbers must be consistent; 2. All pages in the block are physically adjacent to each other.
Flash data recovery tool is to reorganize and recover data based on the data block structure in the Flash chip.