磁盘知识体系

1.磁盘的物理结构（外部结构和内部结构）工作原理

01.外部结构

磁盘主轴：决定磁盘转速（rpm-round per minute）
家用磁盘转速
         7200 rpm
         5400 rpm
企业磁盘转速
        15k rpm
        10k rpm
磁盘盘片：用于存储数据
磁盘磁头：用于读取数据
磁盘接口：用于连接主板

02.硬盘接

a.SATA

b.SCSI

c.PCI-E

03.磁盘的内部结构

a .磁盘（Disk）

b .磁头（Head）

作用说明：用来写入和读取数据的特点说明：盘面数量等于磁头数量工作原理：采用径向运动读写数据

c .磁道（Track）

作用说明：用来存储用户数据特点说明：由多个同心圆组成存储计数：最外面同心圆为0磁道工作原理：磁盘默认按照磁道寻找数据重点原理：磁头径向运动为机械运动（寻道）性能小于固态硬盘(芯片) 原理特点：磁头机械运动较慢

d .扇区（Sector）

作用说明：用来存储用户数据特点说明：磁盘存储最小单位存储计数：默认磁盘扇区从1扇区开始，扇区大小为512字节系统存储最小单位是block

e .柱面（Cylinder）

作用说明：用来存储用户数据特点说明：不同盘面上相同的磁道组成（圆柱体）工作原理：磁盘默认按照柱面进行读写重点原理：磁头之间的切换为电子切换原理特点：磁头电子切换较快

f .单元块（Units）

作用说明：用来存储用户数据特点说明：表示单个柱面大小

04.根据磁盘内部结构计算磁盘大小

磁盘大小=柱面大小（Units）*柱面数量命令运算方法01：echo 柱面大小（Units）*柱面数量|bc 命令运算方法02：awk ‘BEGIN{print 柱面大小（Units）*柱面数量}’ 磁盘大小=（每磁道扇区数*磁头数）柱面数量512字节

[root@shuai ~]# fdisk -l   #显示分区大小

Disk /dev/sda: 53.7 GB, 53687091200 bytes, 104857600 sectors
显示磁头数，扇区数/每磁道数， 柱面数
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x00019671

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      411647      204800   83  Linux
/dev/sda2          411648     8800255     4194304   82  Linux swap / Solaris
/dev/sda3         8800256   104857599    48028672   83  Linux

2.磁盘阵列说明（raid0、raid1、raid5、raid10、raid01）

01.磁盘阵列的作用

a.提高磁盘存储效率

b.提高磁盘存储安全

c.提高磁盘存储容量

02.磁盘整列的配置

a.配置教程：https://baijiahao.baidu.com/s?id=1660694650150042596&wfr=spider&for=pc

b.raid0：存储数据效率高，存储安全性低（至少1块磁盘）

c.raid1：存储数据效率低，存储安全性高（至少2块磁盘）

d.raid5：存储数据效率较高，存储安全性较高（至少要有3块磁盘才能配置，只能坏一块磁盘，损耗一块磁盘容量，3块600G硬盘，实际容量1.2T）

f.raid10：数据存储效率提高，数据安全保障提高（需要RAID10需要4 + 2*N 个磁盘（至少4块），硬盘容量损耗，例如 4 个 250G 的硬盘使用RAID10 阵列，实际容量是 500G。）

g.raid01：数据存储效率提高，数据安全保障提高（需要RAID01需要4 + 2*N 个磁盘（至少4块），硬盘容量损耗，例如 4 个 250G 的硬盘使用RAID10 阵列，实际容量是 500G。）

03.配置LVM（逻辑卷）

实现分区可以弹性扩容和缩容

https://www.cnblogs.com/diantong/p/10554831.html

3.磁盘分区概念

01.MBR结构

02.系统启动引导记录–

MBR引导记录用于引导磁盘空间小于2T GPT引导记录用于引导磁盘空间大于2T

03 分区方式

情况一: 可以划分4个主分区 /dev/sda /dev/sda1 .. sda4 mount /dev/sda1 /mnt 情况二: 可以划分3个主分区 /dev/sda /dev/sda1 .. sda3 可以划分1个扩展分区扩展分区无法直接使用需要在扩展分区基础上划分逻辑分区: /dev/sda5 /dev/sda6 …

04.磁盘分区方法

1.情况一：<2T

a.添加一块硬盘

b.在系统中检查是否识别到了新硬盘

[root@shuai ~]# ll /dev/sdb 
brw-rw---- 1 root disk 8, 16 Jul 21 11:00 /dev/sdb

c.对硬盘进行分区

[root@shuai ~]# fdisk -l  #查看分区
################################################
[root@shuai ~]#  fdisk /dev/sdb（进行分区）
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x339e5789.

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         #删除分区
   g   create a new empty GPT partition table  #创建一个新的GPT分区表
   G   create an IRIX (SGI) partition table
   l   list known partition types    #列出可以分区的类型
   m   print this menu         #打印操作方法
   n   add a new partition     #新建分区
   o   create a new empty DOS partition table
   p   print the partition table #输出分区的结果
   q   quit without saving changes  #不保存退出
   s   create a new empty Sun disklabel  
   t   change a partition's system id #改变分区类型（LVM或增加swmp分区）
   u   change display/entry units  #改变分区方式
   v   verify the partition table  
   w   write table to disk and exit  #保存分区信息并退出
   x   extra functionality (experts only)
#################################################
#开始分区
Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)  #主分区
   e   extended      #逻辑分区
Select (default p): p                                  #选择主分区
Partition number (1-4, default 1): 1
First sector (2048-20971519, default 2048):            #直接回车
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): +1G
Partition 1 of type Linux and of size 1 GiB is set
#检查分区
Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x339e5789

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     2099199     1048576   83  Linux
#扩展分区
Command (m for help): n       
Partition type:
   p   primary (3 primary, 0 extended, 1 free)
   e   extended
Select (default e): e
Selected partition 4
First sector (6293504-20971519, default 6293504): 
Using default value 6293504
Last sector, +sectors or +size{K,M,G} (6293504-20971519, default 20971519): 
Using default value 20971519
Partition 4 of type Extended and of size 7 GiB is set
Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x7ec18600

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     2099199     1048576   83  Linux
/dev/sdb2         2099200     4196351     1048576   83  Linux
/dev/sdb3         4196352     6293503     1048576   83  Linux
/dev/sdb4         6293504    20971519     7339008    5  Extended   #扩展分区
#创建逻辑分区（有了扩展分区才能创建逻辑分区）
Command (m for help): n
All primary partitions are in use
Adding logical partition 5
First sector (6295552-20971519, default 6295552): 
Using default value 6295552
Last sector, +sectors or +size{K,M,G} (6295552-20971519, default 20971519): +1G
Partition 5 of type Linux and of size 1 GiB is set

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x7ec18600

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     2099199     1048576   83  Linux
/dev/sdb2         2099200     4196351     1048576   83  Linux
/dev/sdb3         4196352     6293503     1048576   83  Linux
/dev/sdb4         6293504    20971519     7339008    5  Extended
/dev/sdb5         6295552     8392703     1048576   83  Linux  （逻辑分区）
#保存退出
Command (m for help): w
[root@shuai ~]# mkfs.xfs /dev/sdb3
meta-data=/dev/sdb3              isize=512    agcount=4, agsize=327680 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=1310720, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
[root@shuai ~]# mount /dev/sdb3 /mnt
[root@shuai ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        46G  2.3G   44G   5% /
devtmpfs        981M     0  981M   0% /dev
tmpfs           992M  4.0K  992M   1% /dev/shm
tmpfs           992M  9.6M  982M   1% /run
tmpfs           992M     0  992M   0% /sys/fs/cgroup
/dev/sda1       197M  102M   95M  52% /boot
tmpfs           199M     0  199M   0% /run/user/0
/dev/sdb3       5.0G   33M  5.0G   1% /mnt
[root@shuai ~]# partprobe /dev/sdb

2.情况二：>2T

a.添加一块硬盘

b.在系统中检查是否识别到了新硬盘

[root@nfs01 ~]# ll /dev/sdb
brw-rw---- 1 root disk 8, 16 Jul 21 12:46 /dev/sdb

c.对硬盘进行分区

[root@nfs01 ~]# parted /dev/sdb
GNU Parted 3.1
Using /dev/sdb
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) help                                                             
  align-check TYPE N                        check partition N for TYPE(min|opt) alignment
  help [COMMAND]                           print general help, or help on COMMAND
  mklabel,mktable LABEL-TYPE               create a new disklabel (partition table)  #创建一个分区表（默认为MBR）
  mkpart PART-TYPE [FS-TYPE] START END     make a partition            #创建一个分区
  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         #显示分区信息
        particular partition
  quit                                     exit program #退出并保存分区设置
  rescue START END                         rescue a lost partition near START and END
  
  resizepart NUMBER END                    resize partition NUMBER
  rm NUMBER                                delete partition NUMBER  #根据编号删除分区
  select DEVICE                            choose the device to edit
  disk_set FLAG STATE                      change the FLAG on selected device
  disk_toggle [FLAG]                       toggle the state of FLAG on selected device
  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
(parted) mklabel gpt            #创建gpt分区表
(parted) print                  #查看分区信息                                               
Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdb: 3221GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start  End  Size  File system  Name  Flags
(parted) mkpart primary 0         2100G #创建分区
                        从哪开始  从哪结束
Ignore/Cancel? Ignore
(parted) print                                                            
Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdb: 3221GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name     Flags
 1      17.4kB  2100GB  2100GB               primary
 #第二个分区
(parted)  (parted) mkpart primary 2100 2200G
Warning: You requested a partition from 2100MB to 2200GB (sectors 4101562..4296875000).
The closest location we can manage is 2100GB to 2200GB (sectors 4101562501..4296875000).
Is this still acceptable to you?
Yes/No? yes
Warning: The resulting partition is not properly aligned for best performance.
Ignore/Cancel? Ignore                                                     
(parted) print                                                            
Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdb: 3221GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name     Flags
 1      17.4kB  2100GB  2100GB               primary
 2      2100GB  2200GB  100GB                primary
 #加载磁盘分区
 [root@shuai ~]# partprobe /dev/sdb

4.磁盘格式化操作（创建文件系统）

创建文件系统：磁盘分区存储数据的方式（C6：ext3/4 C7:xfs）

C6：ext3/4

C7:xfs 格式化效率较高，数据存储效率提升

[root@shuai ~]# mkfs.xfs /dev/sdb3
meta-data=/dev/sdb3              isize=512    agcount=4, agsize=327680 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=1310720, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

5.磁盘维护管理知识（如何使用磁盘，挂载）

1.手动挂载

[root@shuai ~]# mount /dev/sdb3 /mnt
[root@shuai ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        46G  2.3G   44G   5% /
devtmpfs        981M     0  981M   0% /dev
tmpfs           992M  4.0K  992M   1% /dev/shm
tmpfs           992M  9.6M  982M   1% /run
tmpfs           992M     0  992M   0% /sys/fs/cgroup
/dev/sda1       197M  102M   95M  52% /boot
tmpfs           199M     0  199M   0% /run/user/0
/dev/sdb3       5.0G   33M  5.0G   1% /mnt
[root@shuai ~]# partprobe /dev/sdb     #让系统可以重新加载识别分区文件

2.自动挂载

 1.将挂载命令放到/etc/rc.local中
[root@shuai ~]# vim /etc/rc.local 
#!/bin/bash
# THIS FILE IS ADDED FOR COMPATIBILITY PURPOSES
#
# It is highly advisable to create own systemd services or udev rules
# to run scripts during boot instead of using this file.
#
# In contrast to previous versions due to parallel execution during boot
# this script will NOT be run after all other services.
#
# Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure
# that this script will be executed during boot.


mount /dev/sdb3 /mnt
~                     
[root@shuai ~]# chmod +x /etc/rc.d/rc.local #添加执行权限
2.在fastab中添加
[root@shuai ~]# blkid（查看磁盘的UUID）
/dev/sda1: UUID="ca74ae85-da75-4df4-a3dc-6e0a0be409e3" TYPE="xfs" 
/dev/sda2: UUID="71913357-a157-4f16-b91f-3339222b0d89" TYPE="swap" 
/dev/sda3: UUID="9a55fc86-daa5-4bcc-88a4-25b69fdd1c92" TYPE="xfs" 
/dev/sdb3: UUID="3d9ec6cd-957b-4578-9279-69704c674b3c" TYPE="xfs" 
/dev/sr0: UUID="2018-05-03-20-55-23-00" LABEL="CentOS 7 x86_64" TYPE="iso9660" PTTYPE="dos"
[root@shuai ~]# tail -1 /etc/fstab 
/dev/sdb2                                 /mnt              xfs     defaults        0            0 
 挂载的磁盘设备                              挂载点          文件类型   挂载参数       是否备份磁盘  是否坚查磁盘
 
 
 说明：挂载参数 mount -o ro /dev/sdb2 /mnt  （只有读的权限）
             mount  -o rw  /dev/sdb2 /mnt （读写的权限）

6.企业常见磁盘问题

（1）磁盘满的情况

[root@nfs01 ~]# dd if=/dev/zero of=/tmp/tt bs=1G count=10
在/tmp/目录中生成一个tt的文件,文件大小10G

报错信息：No space left on device

存储数据过多，block存储空间不足

解决办法：a.删除没用的数据
        b.找出大的数据

[root@nfs01 ~]# du -sh /* |sort -h
[root@nfs01 ~]# find / -type f -size +400M

存储数据过多，inode存储空间不足