A cache memory cache fastest and most expensive storage medium managed by the computer system hardware its use
A main memory storing main memory data storage medium can be processed, the personal computer is typically a few G (after power failure or system crash data will be lost)
The flash memory is different from the local main memory of flash memory is that data is not lost after the power is turned off (widely used in the USB, serial data bus Universal Serial Bus), flash memory, disk storage is also used as a substitute, such as SSDs (solid-state drive)
Disk storage media for magnetic-disk storage, disk capacity, long-term storage of data at a rate of 50% annual growth
Optical storge optical storage is the most popular form of disc Compack disk CD, 700MB data can be stored, play about 80 minutes. Digital Video Disc Digital Video Disk dvd each side can store 4.7GB or 8.5GB of data. Blu Blu-ray single 27GB can store
data of 54GB or bilayer.
Operating in parallel using RAID redundant array of independent disks matrix redundant array independent disk using a plurality of small disks of large disk Alternatively, in a simultaneous manner to reduce costs and improve efficiency.
Improve reliability through redundant disks, redundant simplest and most efficient way information is mirrored, and each one requires a redundant copy of the disk.
Increase efficiency by improving the efficiency of the parallel, data splitting (striping data) on the plurality of magnetic disks, the general implementation is bit bytes are separated (Striping bit-resolution bit-level), such as a disks 8 array, then the data which is a typical magnetic disk storage eight times, and a processing speed is eight times the disk.
Database file organization
Is mapped to a plurality of different database file (File), each fixed length file into a storage unit, the basic unit of block (Block), block storage allocation and data transmission, most of the database is created to allow the block size designation .
Fixed-length record
Each block stores only records which can fully accommodate the longest, and the remaining space is no longer used (to prevent a query record spans multiple blocks)
when a record is deleted, its storage space is idle, then the insert will reuse the space
Documented structure
Sequential file structure
Sequentially ordered set a search code file structure (search code search key is one or more attributes