1-磁盘基础

2016.6.11

磁盘结构

• 硬盘的物理结构

  • 盘片(platter)：硬盘有多个盘片，每盘片2面
  • 磁头(head)：每面一个磁头

• 磁盘的数据结构

  • 扇区：盘片被分为多个扇形区域，每个扇区存放512字节的数据
  • 磁道：同一盘片不同半径的同心圆
  • 柱面：不同盘片相同半径构成的圆柱面

磁盘结构

• 硬盘存储容量=磁头数x磁道（柱面）数x每道扇区数x每扇区字节数
• 可以用柱面/磁头/扇区来唯一定位磁盘上每一个区域

磁盘接口类型

• IDE（并口）
• SATA（串口）
  • 速度快
  • 纠错能力强
• SCSI
  • 转速快
  • CPU占用资源低
  • 支持热插拔

[root@test2 jason]# fdisk -l

Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000d0a36

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        2611    20458496   8e  Linux LVM

Disk /dev/mapper/vg_jason-lv_root: 18.8 GB, 18798870528 bytes
255 heads, 63 sectors/track, 2285 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/mapper/vg_jason-lv_swap: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

[root@test2 jason]#