Linux系统磁盘

所有有系统都一样，都是一种软件被安装于某个硬件之上，这个硬件无外非是一种存储设备，通常操作系统都是安装在磁盘中，所以Linux系统也是一样，都是安装在磁盘中，但是它与Windows系统不一样，因为Linux都是需要创建文件系统才可以使用。

1、  磁盘分类

　　目前市场上的磁盘分类有：IDE磁盘（多用于PC机）、SATA磁盘、SAS磁盘、SSD磁盘等这么几种分类，企业中服务器大多为后面的两种，SATA磁盘多用于企业内部的一些业务、SAS磁盘多用于对外的业务（一些业务平台）。

　　SATA磁盘目前容量最大为4T、SAS磁盘一般都在300G--600G居多，企业生产环境中使用也最多的是这种容量的，实际生产中磁盘的使用主要是看性能需求，也就是磁盘的读写速度。

2、  磁盘的体系结构

企业级服务器多块磁盘的情况

3、  磁盘容量的计算

磁盘的结构一般包括磁道、盘面、扇区、碰头等

一个磁道的大小=512 字节*扇区数
一个盘面的大小=磁道的大小*磁道数
一个磁盘的大小=盘面大小*磁头数
因此
一个磁盘的容量=512 字节*扇区数*磁道数*磁头数

4、  磁盘分区

所有磁盘的分区信息都是存储在分区表中，Linux系统仅支持4个分区表信息（主分区+扩展分区），一个分区表的大小在64bytes

Linux一般分为三个分区分别是：boot分区、swap分区、/根分区

Linux的分区编号：主分区1-4，逻辑分区从5开始计算

实际生产环境分区要求

　　1、  最少要有/和swap两个分区

　　2、  swap（虚拟内存）=1.5*物理内存大小，一般大小于或等于16G的物理内存的服务器，swap分区一般都直接设置为16G大小

　　3、  建议设置/boot分区，Linux引导分区，如内核文件等，一般所有文件一共才几十M的大小，因此这个分区就设置为100-200M即可

5、  磁盘分区工具fdisk

fdisk是针对磁盘容量小于2T

[root@cairui ~]# fdisk --help
fdisk: invalid option -- '-'

fdisk: Usage:
 fdisk [options] <disk>    change partition table
 fdisk [options] -l <disk> list partition table(s)
 fdisk -s <partition>      give partition size(s) in blocks

Options:
 -b <size>                 sector size (, ,  or )
 -c                        switch off DOS-compatible mode
 -h                        print help
 -u <size>                 give sizes in sectors instead of cylinders
 -v                        print version
 -C <number>               specify the number of cylinders
 -H <number>               specify the number of heads
 -S <number>               specify the number of sectors per track

: Success

[root@localhost ~]# fdisk /dev/sda1　　#对/dev/sda1进行分区操作
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x02fadd9c.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table  will be corrected by w(rite)

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition　　#删除一个分区
   l   list known partition types
   m   print this menu
   n   add a new partition　　#新建一个分区
   o   create a new empty DOS partition table
   p   print the partition table　　#打印出分区表信息
   q   quit without saving changes　　#不保存退出
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit　　#将分区信息写入分区表并退出程序
   x   extra functionality (experts only)

Command action
e extended
p primary partition (-)
p
Partition number (-):
First cylinder (-, default ): 设置起始柱面
Using default value
Last cylinder, +cylinders or +size{K,M,G} (-, default ):
设置大小或柱面
Using default value
Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
Command (m for help): p 打印分区表信息
Disk /dev/sdb: 21.5 GB,  bytes
 heads,  sectors/track,  cylinders
Units = cylinders of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
 /
I/O size (minimum/optimal):  bytes /  bytes
Disk identifier: 0xb712cc55
Device Boot Start End Blocks Id System
/dev/sdb1   +  Linux
分区完成后执行 partprobe 通知系统分区表发生改变
接下来进行格式化分区
[root@Centos ~]# mkfs.ext3 /dev/sdb1
mke2fs 1.41. (-May-)
Filesystem label=
OS type: Linux
Block size= (log=)
Fragment size= (log=)
Stride= blocks, Stripe width= blocks
 inodes,  blocks
 blocks (5.00%) reserved for the super user
First data block=
Maximum filesystem blocks=
 block groups
 blocks per group,  fragments per group
 inodes per group
Superblock backups stored on blocks:
, , , , , , , , ,

Writing inode tables: done
Creating journal ( blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every  mounts or
 days, whichever comes first. Use tune2fs -c or -i to override.
[root@Centos ~]# tune2fs -c - /dev/sdb1
tune2fs 1.41. (-May-)
Setting maximal mount count to -
[root@Centos ~]# mount /dev/sdb1 /mnt 挂载分区至/mnt 下
[root@Centos ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 50G .5G 44G % /
tmpfs 932M  932M % /dev/shm
/dev/sda1 485M 39M 421M % /boot
 /
/dev/mapper/VolGroup-lv_home 26G 215M 24G % /home
/dev/sdb1 20G 172M 19G % /mnt

6、  磁盘分区工具parted

由于环境限制无法有2T或者以上大小的磁盘，只能模拟环境来使用parted分区工具来进行分区

[root@Centos ~]# parted /dev/sdb mklabel gpt
将磁盘转换成 gpt 的格式
[root@Centos ~]# parted /dev/sdb mkpart primary  （200M）
Warning: The resulting partition is not properly aligned for best
performance.
Ignore/Cancel? Ignore
[root@Centos ~]# parted /dev/sdb p 打印分区表信息
Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdb: 1074MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
 .4kB 200MB 200MB primary
[root@Centos ~]# parted /dev/sdb mkpart primary
分区并设置大小
Information: You may need to update /etc/fstab.
[root@Centos ~]# parted /dev/sdb p 打印分区表信息
Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdb: 1074MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
 .4kB 200MB 200MB primary
 201MB 1073MB 871MB primary
[root@Centos ~]# mkfs.ext4 /dev/sdb1
mke2fs 1.41. (-May-)
Filesystem label=
OS type: Linux
Block size= (log=)
Fragment size= (log=)
 /
Stride= blocks, Stripe width= blocks
 inodes,  blocks
 blocks (5.00%) reserved for the super user
First data block=
Maximum filesystem blocks=
 block groups
 blocks per group,  fragments per group
 inodes per group
Superblock backups stored on blocks:
, , , ,
Writing inode tables: done
Creating journal ( blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every  mounts or
 days, whichever comes first. Use tune2fs -c or -i to override.
[root@Centos ~]# tune2fs -c - /dev/sdb1
tune2fs 1.41. (-May-)
Setting maximal mount count to -
[root@Centos ~]# mount /dev/sdb1 /mnt
[root@Centos ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root 50G .5G 44G % /
tmpfs 932M  932M % /dev/shm
/dev/sda1 485M 39M 421M % /boot
/dev/mapper/VolGroup-lv_home 26G 215M 24G % /home
/dev/sdb1 185M 5.6M 170M % /mnt

[root@cairui ~]# parted --help
Usage: parted [OPTION]... [DEVICE [COMMAND [PARAMETERS]...]...]
Apply COMMANDs with PARAMETERS to DEVICE.  If no COMMAND(s) are given, run in
interactive mode.

OPTIONs:
  -h, --help                      displays this help message
  -l, --list                      lists partition layout on all block devices
  -m, --machine                   displays machine parseable output
  -s, --script                    never prompts for user intervention
  -v, --version                   displays the version
  -a, --align=[none|cyl|min|opt]  alignment for new partitions

COMMANDs:
  align-check TYPE N                        check partition N for TYPE(min|opt)
        alignment
  check NUMBER                             do a simple check on the file system
  cp [FROM-DEVICE] FROM-NUMBER TO-NUMBER   copy file system to another partition
  help [COMMAND]                           print general help, or help on
        COMMAND
  mklabel,mktable LABEL-TYPE               create a new disklabel (partition
        table)
  mkfs NUMBER FS-TYPE                      make a FS-TYPE file system on
        partition NUMBER
  mkpart PART-TYPE [FS-TYPE] START END     make a partition
  mkpartfs PART-TYPE FS-TYPE START END     make a partition with a file system
  move NUMBER START END                    move partition NUMBER
  name NUMBER NAME                         name partition NUMBER as NAME
  print [devices|free|list,all|NUMBER]     display the partition table,
        available devices, free space, all found partitions, or a particular
        partition
  quit                                     exit program
  rescue START END                         rescue a lost partition near START
        and END
  resize NUMBER START END                  resize partition NUMBER and its file
        system
  rm NUMBER                                delete partition NUMBER
  select DEVICE                            choose the device to edit
  set NUMBER FLAG STATE                    change the FLAG on partition NUMBER
  toggle [NUMBER [FLAG]]                   toggle the state of FLAG on partition
        NUMBER
  unit UNIT                                set the default unit to UNIT
  version                                  display the version number and
        copyright information of GNU Parted