"FSFA Reading Notes" Ch 2 computer foundatinons (2)

Hard Disk Technology

1. Mechanical hard disk internal construction Several important concepts: Sector (Sector), head (read-write head), track (tracks), Cylinder (cylinder).　　　　　　　　If a file is larger, the disk is written in the following order, so there is a subsequent CHS address representation: Disk rotation full of one sector, write full one track, write the next sector of the same track, and write the next disk (the next read and write head), write a cylindrical face Dynamic arm radial movement, write the next cylinder, write the entire file this is based on the rotational wait (latency) time << seek (seek) time design, the moving time of the boom is slower than the rotating shaft rotation. (say this originally was in the data structure comprehensive design class to understand, when speaking outside the row) disk structure diagram:  2. The interface of the mechanical hard drive is used for PC's common SATA (Serial Advanced Technology Attachment), Serial ATA, which is an interface specification.　　ATA-Spec disks can be IDE disk. In contrast, the SCSI (Small computer Systems Interface) interface specification is commonly used for servers. For the SATA interface, the two sets of pins are independent of the ~ 3. The representation of the sector address CHS is replaced by LBA, but the boot record in order to backward-compatible still records the value of CHS, sometimes encountered only the CHS file system or data structure, need to manually convert LBA with the following formula (((CYLINDER * heads_per_cylinder) + HEAD ) * Sectors_per_track) + SECTOR-1 (to overcome the 8.1GB limit associated with translation, the CHS addresses Were a bandoned, and Logical Block Addresses (LBA) became Standard. lba uses a single number, starting at 0, to address Each sector and have been supported since the first Formal ata specification.)

"FSFA Reading Notes" Ch 2 computer foundatinons (2)