data blockIt is a group of records arranged together in sequence. YesMain memoryAnd inputoutput deviceorExternal memoryA unit of data transmitted between.It is the physical record of the data, andLogical record(Logically related, instorageThere are three ways of correspondence between the data units occupying a group of adjacent units on the): ① a block is a record; ②A block contains several logical records; ③A logical record occupies several blocks.The size of data blocks can be fixed or variable, and there is a gap between blocks.The design data block size is affected by many factors, including input and output efficiency,storage space Cost and computer application characteristics.
Main storage andcacheThey are divided into data blocks with equal growth. Every time the main memory and cache exchange data, the data blocks are taken as units.[1]
In SQL Server:
In text, ntext, and image data, data blocks are transferred once between the application and the SQL Server instanceData unit。The term also applies toStorage unit。On tapeBackup filesIn, a data block is a unit of physical I/O.
Data block in Flash chip
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The concept of data block in the Flash chip is a logical concept, but different from the physical parameters referred to by the chip, it is specifically composed of adjacent pages with the same data ID number and continuous physical positions.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 that make up each block may be different, or a page may make up a block, and multiple pages make up a block.
The data block concept of Flash chip is an abstract concept, which must have the following characteristics:
1. The ID numbers are the same, that is, the ID numbers of all pages in the same data block must be the same;2. All pages within a block are physically adjacent.
The Flash data recovery tool is based on the data block structure in the Flash chip for data reorganization and recovery.
