硬盘技术：磁道,扇区,柱面和磁头数

硬盘技术：磁道,扇区,柱面和磁头数 硬盘技术:磁道,扇区,柱面和磁头数 Hard disk technology: tracks, sectors, cylinders, and heads..txt did your mom throw them up when you were born and keep the placenta big? Don't treat shrimps as seafood. Don't treat shrimps as seafood. 1. tracks, sectors, cylinders, and heads The basic component of a hard disk is a disk made of hard metal material coated with magnetic medium, varying in number of disks of different capacities. Each disk has two sides that record information. The disk is divided into many fan-shaped regions, each of which is called a sector. Each sector can store 128 * 2 N times (N = 0.1.2.3) byte information. In DOS, each sector is 128 * 2 of the 2 square = 512 bytes, the disk surface with the center of the disk as the center, concentric rings of different radii are called tracks. A cylinder consisting of tracks of the same radius and different disks in a hard disk is called a cylinder. Track and cylinder are different radius of the circle, on many occasions, track and cylinder can be used interchangeably, we know that each disk has two faces, each face has a head, head number used to distinguish. Sectors, tracks (or cylinders) and number of magnetic heads form the basic parameters of the hard disk structure, and the capacity of the hard disk can be obtained by using these parameters: Storage capacity = head number * track (cylinder) number * per sector number * per sector byte Main points: (1) the hard disk has several disks, each of which has two planes, each with a magnetic head (2) the disk is divided into several sectors, namely sector (3) concentric circles with different radii on the same disk are tracks (4) cylindrical surface with different radii, namely cylinder; (5) formula: storage capacity = magnetic head number * track (cylinder) number * per sector number * per sector byte number (6) the information records can be represented as * * tracks (cylinders), * heads, * * sectors The 2. cluster A cluster is the smallest unit in which DOS is assigned. When a small file is created, such as a byte, it does not take up only one byte of space on disk, but occupies the entire cluster. DOS depending on the storage medium (such as floppy disk, hard disk), different capacity of the hard disk, the size of the cluster is not the same. The size of the cluster can be obtained in the disk parameter block (BPB). The concept of clusters applies only to data regions. This point: (1) the cluster is the smallest unit for DOS allocation. (2) different storage media, different capacity hard disk, different DOS version, the size of cluster is not the same. (3) the concept of clusters applies only to data regions. 3. sector number definition: absolute sector and DOS sector Introduce according to the front, we can use the cylinder / head / sector to every area of the unique location on the disk, or that every cylinder / head / disk sector sector and corresponding relation, usually DOS cylinder / head / sector "such a representation called" absolute sector "representation. But DOS cannot use absolute sector to manage the information on disk instead of using the so-called "relative sector" or "DOS sector"". The relative sector is just a number, such as cylinder 140, head 3, and sector 4 corresponding to the sector number 2757. The number is in one-to-one correspondence with the absolute sector "cylinder / head / sector". When using the relative sector number, DOS is from the cylinder 0, head 1, sector 1 starts (Note: cylinder 0, head 0, sector 1 no DOS sector number, DOS cannot access, BIOS can be called the first visit), DOS sector number is 0, the remaining sector number is 1 to the track 16 (17 per sector), then the head number is 2, 17 for cylindrical sector 0, the formation of the DOS sector, from 17 to 33. All heads of the cylinder. Then move to cylinder 1, head 1, sector 1 to continue the numbering of the DOS sector, that is, according to the fan area code, head number, cylinder number (track number) in the order of growth, the continuous distribution of DOS fan area code. Formula: remember the first head number DH DOS sector Cylinder number DC first DOS sector The first DS DOS sector sector NS sectors per track The total number of NH disk head The relative sector number of a sector (cylinder C, head H, sector S) is RS: RS = NH * NS * (CDC) NS * (HDH) + (SDS) If RS, DC, DH, DS, NS, and NH are known, then S = (RS MOD NS) DS (H = (RS DIV NS) MOD NH) DH (C = (RS DIV NS) DIV NH) DC Main points: (1) the absolute sector represented by cylinder / head / sector is also called physical disk address (2) a single digit represents the relative sector or DOS sector, also known as the logical fan code (3) conversion formula between relative sector and absolute sector 4.DOS partition of disk area A formatted hard disk, the disk according to the data records of different function can be divided into the main boot record (MBR:Main Boot Record), Dos (DBR:Dos Boot Record) boot record, file allocation table (FAT:File Assign Table), the root directory (BD:Boot Directory) and the data area. The first 5 important information on the outer track of the disk, the reason is that the perimeter of the outer ring is greater than the perimeter of the inner ring, that is to say, the storage density of the outer ring is smaller and the reliability is higher. Main points: (1) the entire disk can be divided into MBR, DBR, FAT, BD, and data areas. (2) MBR, DBR, FAT, and BD on the disk. 5.MBR MBR is located in the first physical sector of the hard disk (absolute sector), cylinder 0, head 0, sector 1. Since the DOS is made up of cylinder 0, head 1, sector 1, the MBR does not belong to the DOS sector, and DOS cannot be accessed directly. MBR contains the main boot and hard disk partition tables for the hard disk. The partition table has 4 partition records. A record area is a table that records information about partitions. It is stored continuously from the main boot record offset address 01BEH, each recording area of 16 bytes. Format of partition table The offset meaning of a partitioned table entry 00 boot designator 1B The head number of the 01 partition boot record 1B The 02 partition guides the sector and cylinder number 2B of the record 04 system designator 1B 05 end of partition head number 1B 06 partition end sector and cylinder number 2B The number of sectors in front of the 08 partition 4B The total number of sectors in the 0C partition 4B Only 4 partitions have 1 active partition, namely C. The symbol is 80H in the first byte of the partitioned table. If 00H, inactive partitions are indicated. Such as: 80010100, 0B, FE, 3F, 81, 3F, 000000, C3, DD, 1F, 00 0000018205, FE, BF, 0C, 02, DE, 1F, 00, 0E, 906100 0000000000000000, 0000000000000000 0000000000000000, 0000000000000000 Main points: (1) MBR is located in the first physical sector of cylinder, cylinder 0, head 0, sector 1. Not part of the DOS sector, (2) the master boot record is divided into the main boot program and the hard disk partition table of the hard disk. 6.DBR DBR is located in cylinder 0, head 1, sector 1, logical sector 0. DBR is divided into two parts: the DOS bootstrap program and the BPB (BIOS parameter block). The DOS boot loader completes the location and loading of the DOS system files (IO.SYS, MSDOS.SYS), while the BPB is used to describe disk information for the DOS partition. BPB is located at DBR offset 0BH, with a total of 13 bytes. It contains logical formatting parameters used for computing DOS, file allocation table on disk, start address directory area and data area, BPB after three words (grid) to provide physical format with some parameters. The boot program or device driver converts the disk logical address (DOS, area code) into physical addresses (absolute fan numbers) based on this information. BPB format Serial offset address meaning 1 03H0AH No. OEM 2 0BH - 0CH bytes per sector 3 0DH per cluster sector number 4 0EH0FH retain the number of sectors 5 10H FAT backup number 6 11H12H root number 7 13H - 14H disk total sector count 8 15H description medium 9 16H17H sectors per FAT 10 18H19H sectors per track 11 1AH1BH head 12 1CH1FH special hidden sectors 13 20H 23H total sector count 14 24H25H physical drive number 15 26H extended boot visa 16 27H2AH volume serial number 17 2BH35H volume label 18 36H3DH file system. DOS boot record formula: The file allocation table and keep the number of sectors The number of root directory = x FAT reserved sector of each FAT sector The data area and the root directory of the logical sector number (32 + X + (directory in the root directory of the number of bytes per sector 1 bytes per sector)) DIV Absolute sectornumber = logical sector number + hidden sector number Sectornumber = (absolute sector number MOD the number of sectors per track) + 1 Head number (DIV = absolute sector number of sectors per track) head number MOD Track number (DIV = absolute sector number of sectors per track) head number DIV Main points: (1) DBR is located in cylinder 0, head 1, sector 1, and its logical area code is 0 (2) DBR contains the DOS boot program and the BPB. (3) BPB is very important, so that the logical address and physical address can be calculated. Seven The directory file name, the first byte in the area, has a special meaning: 00H stands for unused 05H stands for actually called E5H "EBH" stands for this file. It has been deleted The meaning of each byte in the directory item property area is as follows: 76543210 The repaired rolls are hidden only With the change of target system of Tibetan reading A record genus Aspiration Note: the long file name of WINDOWS uses the "reserved" area as mentioned in the previous table. Main points: (1) the file directory is the record of all files, subdirectories, extensions, attributes, and the creation or deletion of the last modified date. The beginning of the cluster number and the length of the file A registration form. (2) the content training listed in DOS is obtained from the file catalog table of DIR. (3) the start number of the file is filled in the file directory, and the other clusters are filled in the position of the upper cluster in the FAT. 9. physical drives and logical drives Physical drive refers to the actual installed drive. A logical drive is generated after formatting the physical drive. Main point: ditto.