Linux系统磁盘管理详解

Linux磁盘管理分为五个步骤：首先在服务器上添加相应的硬盘（如/dev/sda、sdb、sdc等），对全新的服务器（即没有操作系统）做硬RAID0、RAID1、RAID5、RAID10或者逻辑卷LVM，然后进行磁盘分区，
创建完分区后进行格式化分区（初始化inode和block），最后就是挂载到linux文件系统中就可以进行安装操作系统或者存放数据

1）    磁盘是按照柱面为单位读写数据的，即先读取同一个盘面的某一个磁道，读完之后，如果数据没有读完，磁头也不会切换其他的磁道，而是选择切换磁头，读取下一个盘面的相同半径的磁道，直到所有盘面的相同半径  的磁道读取完成之后，如果数据还没有读写完成，才会切换其他不同半径的磁道，这个切换磁道的过程称为寻道  2）    不同磁头间的切换是电子切换，而不同磁道间的切换需要磁头做径向运动，这个径向运动需要步进电机调节，这个动作是机械的切换  3）    磁头寻道是机械运动，切换磁头是电子切换

1）    给磁盘分区的实质就是针对上述0磁头0磁道1扇区的前446字节之后的64bytes的分区表进行设置，即主要是划分起始以及结束磁头号、扇区号即柱面号  2）    给磁盘分区的工具有fdisk（适合给小于2TB的磁盘分区），parted（擅长给大于2TB的磁盘分区，也可以对小于2TB的磁盘分区），首选fdisk，只有磁盘大于2TB时才去选parted  补充：（企业面试题：一台服务器6块600G的磁盘，raid5后，总大小3TB，此时无法安装系统，请问为什么？）  解决办法：  方法1：做raid5后，不要重启装系统，而是再回到raid界面，继续分1个小的虚拟磁盘vd 200G，用这个200G的虚拟磁盘装系统，装完系统后再把剩余的2.8T分区通过parted  方法2：先拿1块盘做raid0，剩下5块盘做raid5，在raid0上安装操作系统  方法3：装系统时，选择gpt分区格式，即可安装操作系统  3）    一块磁盘的分区表仅有64bytes大小，每个分区表要占用16字节，因此一块硬盘仅支持四个分区表信息，即主分区+扩展分区的总量不超过4个  4）    磁盘分区是按照柱面（cylinder）来划分的  5）    扩展分区不能直接使用，需要在扩展分区的基础上创建逻辑分区才行  6）    扩展分区有自己的分区表，因此扩展分区下面的逻辑分区可以有多个  磁盘在使用前一般要进行分区，当然如果不分区直接格式化使用也是没问题的，但这不是常见情况；磁盘分区有主分区、扩展分区和逻辑分区之分；一块硬盘最多可以有4个分区表信息（磁盘本身限制），其中一个主分区的
位置可以用一个扩展分区替换，且一块硬盘只能有一个扩展分区（操作系统限制），在这个扩展分区内可以划分多个逻辑分区（IDE磁盘逻辑分区大概编号可以是5-63，SATA编号5-15）

RAID是廉价的冗余磁盘阵列（Redundant Array of Inexpensive Disk）的简称，有时也简称磁盘阵列（Disk Array）  RAID是一种把多块独立的物理磁盘按不同的技术方式组合起来形成一个磁盘组，在逻辑上（做完RAID，装系统后）看起来就是一块大的磁盘，可以提供比单个物理磁盘更大的存储容量或更高的存储性能，
同时又能提供不同级别数据冗余备份的一种技术  RAID技术分类：基于硬件的RAID技术和基于软件的RAID技术

LVM全称（Logic Volume Management）逻辑卷管理，最大用途是可以灵活的管理磁盘的容量，让磁盘分区可以随意的放大或者缩小，便于更好的应用磁盘的剩余空间  LVM是在硬盘的分区之上，创建一个逻辑层，以方便系统管理整个硬盘分区系统。LVM最先是由IBM开发，在AIX系统上实现，OS/2操作系统与HP-UX也支持这个功能。在1998年，HeinzMauelshagen
根据在HP-UX上的LVM管理器，写出第一个linux版本

LVM：灵活的管理磁盘的容量，有一定的冗余和性能功能，但是很弱  RAID：更侧重于性能和数据安全  如果过于强调性能与备份，那么还是应该使用RAID功能，而不是LVM

1）    提升数据安全性  2）    提升数据读写性能  3）    提供更大的单一逻辑磁盘数据容量存储

MBR分区方式：无法支持超过2TB的硬盘的分区（或单个分区超过2TB）  GPT分区方式：很好的解决了传统MBR无法逾越2TB的限制，如果大于2TB就用GPT分区  Fdisk命令无法支持gpt分区格式，Parted命令操作是实时的

[root@cobbler-node1 ~]# fdisk -l /dev/sdb     Disk /dev/sdb: 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: 0x000a3ee6       Device Boot      Start         End      Blocks   Id  System  [root@cobbler-node1 ~]# fdisk -cu /dev/sdb    Command (m for help): n  Command action     e   extended     p   primary partition (1-4)  p  Partition number (1-4): 1  First sector (2048-4194303, default 2048):   Using default value 2048  Last sector, +sectors or +size{K,M,G} (2048-4194303, default 4194303): +100M    Command (m for help): n    Command action     e   extended     p   primary partition (1-4)  p  Partition number (1-4): 2  First sector (206848-4194303, default 206848):   Using default value 206848  Last sector, +sectors or +size{K,M,G} (206848-4194303, default 4194303): +100M    Command (m for help): n  Command action     e   extended     p   primary partition (1-4)  p  Partition number (1-4): 3  First sector (411648-4194303, default 411648):   Using default value 411648  Last sector, +sectors or +size{K,M,G} (411648-4194303, default 4194303): +100M    Command (m for help): n  Command action     e   extended     p   primary partition (1-4)  e  Selected partition 4  First sector (616448-4194303, default 616448):   Using default value 616448  Last sector, +sectors or +size{K,M,G} (616448-4194303, default 4194303):   Using default value 4194303    Command (m for help): n  First sector (618496-4194303, default 618496):   Using default value 618496  Last sector, +sectors or +size{K,M,G} (618496-4194303, default 4194303): +100M    Command (m for help): p    Disk /dev/sdb: 2147 MB, 2147483648 bytes  255 heads, 63 sectors/track, 261 cylinders, total 4194304 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 identifier: 0x000a3ee6       Device Boot      Start         End      Blocks   Id  System  /dev/sdb1            2048      206847      102400   83  Linux  /dev/sdb2          206848      411647      102400   83  Linux  /dev/sdb3          411648      616447      102400   83  Linux  /dev/sdb4          616448     4194303     1788928    5  Extended  /dev/sdb5          618496      823295      102400   83  Linux    Command (m for help): w  The partition table has been altered!    Calling ioctl() to re-read partition table.  Syncing disks.  #格式化/dev/sdb5分区文件系统为ext4类型  [root@cobbler-node1 ~]# mkfs.ext4 /dev/sdb5  mke2fs 1.41.12 (17-May-2010)  Filesystem label=  OS type: Linux  Block size=1024 (log=0)  Fragment size=1024 (log=0)  Stride=0 blocks, Stripe width=0 blocks  25688 inodes, 102400 blocks  5120 blocks (5.00%) reserved for the super user  First data block=1  Maximum filesystem blocks=67371008  13 block groups  8192 blocks per group, 8192 fragments per group  1976 inodes per group  Superblock backups stored on blocks:           8193, 24577, 40961, 57345, 73729    Writing inode tables: done                              Creating journal (4096 blocks): done  Writing superblocks and filesystem accounting information: done    This filesystem will be automatically checked every 38 mounts or  180 days, whichever comes first.  Use tune2fs -c or -i to override.  #打印块设备的属性信息  [root@cobbler-node1 ~]# blkid /dev/sdb5  /dev/sdb5: UUID="20cdc54d-f801-4399-9799-f92daac43155" TYPE="ext4"   #创建挂载目录  [root@cobbler-node1 ~]# mkdir /applog  #挂载/dev/sdb5到/applog目录  [root@cobbler-node1 ~]# mount /dev/sdb5 /applog  #验证/dev/sdb5是否挂载成功  [root@cobbler-node1 ~]# df -h | grep "applog"  /dev/sdb5        97M  5.6M   87M   7% /applog  #加载开机启动自动挂载/dev/sdb5  [root@cobbler-node1 ~]# echo "UUID=20cdc54d-f801-4399-9799-f92daac43155 /applog ext4 defaults 0 0" >> /etc/fstab  [root@cobbler-node1 ~]# tail -1 /etc/fstab   UUID=20cdc54d-f801-4399-9799-f92daac43155 /applog ext4 defaults 0 0  #查看/dev/sdb磁盘的现有分区  [root@cobbler-node1 ~]# fdisk -l /dev/sdb    Disk /dev/sdb: 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: 0x000a3ee6       Device Boot      Start         End      Blocks   Id  System  /dev/sdb1               1          13      102400   83  Linux  Partition 1 does not end on cylinder boundary.  /dev/sdb2              13          26      102400   83  Linux  Partition 2 does not end on cylinder boundary.  /dev/sdb3              26          39      102400   83  Linux  Partition 3 does not end on cylinder boundary.  /dev/sdb4              39         262     1788928    5  Extended  Partition 4 does not end on cylinder boundary.  /dev/sdb5              39          52      102400   83  Linux  注意：其他分区如：/dev/sdb1、/dev/sdb2、/dev/sdb3格式化创建文件系统、创建挂载目录并挂载到相应的目录、加载开机自启动，请参照/dev/sdb5的操作即可

#parted交互式方式创建磁盘分区（parted操作是实时生效的）  [root@cobbler-node1 ~]# parted /dev/sdb  GNU Parted 2.1  Using /dev/sdb  Welcome to GNU Parted! Type 'help' to view a list of commands.  (parted) mklabel gpt                                                        Warning: The existing disk label on /dev/sdb will be destroyed and all data on this disk will be lost. Do you want to continue?  Yes/No? yes                                                                 (parted) mkpart primary 0 100                                               Warning: The resulting partition is not properly aligned for best performance.  Ignore/Cancel? Ignore                                                       (parted) mkpart primary linux-swap 101 201                                  (parted) mkpart logical ext4 202 302                                        (parted) p                                                                  Model: VMware, VMware Virtual S (scsi)  Disk /dev/sdb: 2147MB  Sector size (logical/physical): 512B/512B  Partition Table: gpt    Number  Start   End    Size    File system  Name     Flags   1      17.4kB  100MB  100MB                primary   2      101MB   201MB  101MB                primary   3      202MB   302MB  99.6MB               logical    (parted) quit                                                               Information: You may need to update /etc/fstab.                             #查看分区是否立即生效  [root@cobbler-node1 ~]# ls /dev/sdb*  /dev/sdb  /dev/sdb1  /dev/sdb2  /dev/sdb3  [root@cobbler-node1 ~]# cat /proc/partitions | grep -w "sdb[0-3]+"      8       17      97639 sdb1     8       18      98304 sdb2     8       19      97280 sdb3  #格式化分区创建文件系统  [root@cobbler-node1 ~]# mkfs.ext4 /dev/sdb3  mke2fs 1.41.12 (17-May-2010)  Filesystem label=  OS type: Linux  Block size=1024 (log=0)  Fragment size=1024 (log=0)  Stride=0 blocks, Stripe width=0 blocks  24384 inodes, 97280 blocks  4864 blocks (5.00%) reserved for the super user  First data block=1  Maximum filesystem blocks=67371008  12 block groups  8192 blocks per group, 8192 fragments per group  2032 inodes per group  Superblock backups stored on blocks:           8193, 24577, 40961, 57345, 73729    Writing inode tables: done                              Creating journal (4096 blocks): done  Writing superblocks and filesystem accounting information: done    This filesystem will be automatically checked every 26 mounts or  180 days, whichever comes first.  Use tune2fs -c or -i to override.  #查看块设备的属性信息  [root@cobbler-node1 ~]# blkid /dev/sdb3  /dev/sdb3: UUID="95f2058c-385e-484b-9f4a-64d62bdd0a98" TYPE="ext4"   #创建挂载目录  [root@cobbler-node1 ~]# mkdir /applog1  #挂载文件系统到相应的目录  [root@cobbler-node1 ~]# mount /dev/sdb3 /applog1  #验证挂载是否成功  [root@cobbler-node1 ~]# df -h | grep "sdb"   /dev/sdb3        92M  5.6M   82M   7% /applog1  #加载文件系统随开机自动挂载  [root@cobbler-node1 ~]# echo "UUID=95f2058c-385e-484b-9f4a-64d62bdd0a98 /applog1 ext4 defaults 0 0" >> /etc/fstab   [root@cobbler-node1 ~]# tail -1 /etc/fstab  UUID=95f2058c-385e-484b-9f4a-64d62bdd0a98 /applog1 ext4 defaults 0 0

parted /dev/sdb mklabel gpt yes  #设置分区表类型为gpt（类型分为两种：msdos与gpt）  parted /dev/sdb mkpart primary 0 100 Ignore #创建主分区100M（单位默认为MB）  parted /dev/sdb mkpart primary linux-swap 101 201 #创建swap分区100M  parted /dev/sdb mkpart logical ext4 202 302 #创建逻辑分区100M，文件系统为ext4  parted /dev/sdb p #显示创建的分区  parted /dev/sdb rm 1 #删除创建的1号分区  parted /dev/sdb rm 2 #删除创建的2号分区  parted /dev/sdb rm 3 #删除创建的3号分区

#创建分区/dev/sdb1  [root@cobbler-node1 ~]# fdisk -cu /dev/sdb    Command (m for help): n   Command action     e   extended     p   primary partition (1-4)  p  Partition number (1-4): 1  First sector (2048-4194303, default 2048):   Using default value 2048  Last sector, +sectors or +size{K,M,G} (2048-4194303, default 4194303): +1G    Command (m for help): p    Disk /dev/sdb: 2147 MB, 2147483648 bytes  255 heads, 63 sectors/track, 261 cylinders, total 4194304 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 identifier: 0x000a3ee6       Device Boot      Start         End      Blocks   Id  System  /dev/sdb1            2048     2099199     1048576   83  Linux    Command (m for help): w  The partition table has been altered!    Calling ioctl() to re-read partition table.  Syncing disks.  #格式化分区类型为swap  [root@cobbler-node1 ~]# mkswap /dev/sdb1  Setting up swapspace version 1, size = 1048572 KiB  no label, UUID=546425d3-0a71-4f5b-9295-10dccee357da  [root@cobbler-node1 ~]# free -m               total       used       free     shared    buffers     cached  Mem:           474         94        380          0         10         30  -/+ buffers/cache:         52        422  Swap:         1023          0       1023  #启用用于分页和交换的设备和文件  [root@cobbler-node1 ~]# swapon /dev/sdb1  [root@cobbler-node1 ~]# free -m               total       used       free     shared    buffers     cached  Mem:           474         94        380          0         10         30  -/+ buffers/cache:         53        421  Swap:         2047          0       2047  #追加到/etc/fstab开机随系统启动  [root@cobbler-node1 ~]# echo "/dev/sdb1 swap swap defaults 0 0" >> /etc/fstab  #显示正在使用的虚拟交换空间  [root@cobbler-node1 ~]# swapon -s             Filename                                Type            Size    Used    Priority  /dev/sda2                               partition       1048568 0       -1  /dev/sdb1                               partition       1048568 0       -2

[root@cobbler-node1 ~]# dd if=/dev/zero of=/tmp/swap bs=10M count=100  100+0 records in  100+0 records out  1048576000 bytes (1.0 GB) copied, 31.7965 s, 33.0 MB/s  [root@cobbler-node1 ~]# ls -ldh /tmp/swap   -rw-r--r-- 1 root root 1000M Jun 23 15:05 /tmp/swap  [root@cobbler-node1 ~]# mkswap /tmp/swap   mkswap: /tmp/swap: warning: don't erase bootbits sectors          on whole disk. Use -f to force.  Setting up swapspace version 1, size = 1023996 KiB  no label, UUID=ea3fe1f1-895c-4885-9e42-78cab304efd1  [root@cobbler-node1 ~]# free -m               total       used       free     shared    buffers     cached  Mem:           474        457         17          0          2        390  -/+ buffers/cache:         64        410  Swap:         2047          0       2047  [root@cobbler-node1 ~]# swapon /tmp/swap   [root@cobbler-node1 ~]# free -m               total       used       free     shared    buffers     cached  Mem:           474        458         16          0          2        390  -/+ buffers/cache:         65        409  Swap:         3047          0       3047  [root@cobbler-node1 ~]# echo "/tmp/swap swap swap defaults 0 0" >> /etc/fstab  #显示正在使用的虚拟交换空间  [root@cobbler-node1 ~]# swapon -s             Filename                                Type            Size    Used    Priority  /dev/sda2                               partition       1048568 0       -1  /dev/sdb1                               partition       1048568 0       -2  /tmp/swap                               file            1023992 0       -3  企业案例场景：  Swap在工作中，特别是java环境，程序写的有问题，会发生内存泄露，可能会被占用，让开发改程序，临时运维加大swap，重启系统

#普通ext4文件系统格式化过程  [root@cobbler-node1 ~]# mkfs -t ext4 -b 4096 -I 256 /dev/sdb3  mke2fs 1.41.12 (17-May-2010)  Filesystem label=  OS type: Linux  Block size=4096 (log=2)  Fragment size=4096 (log=2)  Stride=0 blocks, Stripe width=0 blocks  24320 inodes, 24320 blocks  1216 blocks (5.00%) reserved for the super user  First data block=0  Maximum filesystem blocks=25165824  1 block group  32768 blocks per group, 32768 fragments per group  24320 inodes per group    Writing inode tables: done                              Creating journal (1024 blocks): done  Writing superblocks and filesystem accounting information: done    This filesystem will be automatically checked every 24 mounts or  180 days, whichever comes first.  Use tune2fs -c or -i to override.  #防止出现上面的告警信息（标黄）  [root@cobbler-node1 ~]# tune2fs -c -1 /dev/sdb3                tune2fs 1.41.12 (17-May-2010)  Setting maximal mount count to -1  #挂载到相应目录  [root@cobbler-node1 ~]# mount -t ext4 /dev/sdb3 /applog1  #显示挂载的文件系统  [root@cobbler-node1 ~]# df -hT  Filesystem     Type     Size  Used Avail Use% Mounted on  /dev/sda3      ext4     8.7G  3.3G  5.1G  40% /  tmpfs          tmpfs    238M     0  238M   0% /dev/shm  /dev/sda1      ext4     194M   29M  155M  16% /boot  /dev/sr0       iso9660  4.2G  4.2G     0 100% /mnt  /dev/sdb3      ext4      90M  4.1M   81M   5% /applog1

# dumpe2fs - dump ext2/ext3/ext4 filesystem information  [root@cobbler-node1 ~]# dumpe2fs /dev/sdb3  dumpe2fs 1.41.12 (17-May-2010)  Filesystem volume name:   <none>  Last mounted on:          <not available>  Filesystem UUID:          23d188bf-7b4c-41c1-a33e-dd908926303f  Filesystem magic number:  0xEF53  Filesystem revision #:    1 (dynamic)  Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg 
dir_nlink extra_isize  Filesystem flags:         signed_directory_hash   Default mount options:    (none)  Filesystem state:         clean  Errors behavior:          Continue  Filesystem OS type:       Linux  Inode count:              24320  Block count:              24320  Reserved block count:     1216  Free blocks:              21761  Free inodes:              24309  First block:              0  Block size:               4096  Fragment size:            4096  Reserved GDT blocks:      5  Blocks per group:         32768  Fragments per group:      32768  Inodes per group:         24320  Inode blocks per group:   1520  Flex block group size:    16  Filesystem created:       Sun Jun 24 15:01:18 2018  Last mount time:          Sun Jun 24 15:05:39 2018  Last write time:          Sun Jun 24 15:05:39 2018  Mount count:              1  Maximum mount count:      -1  Last checked:             Sun Jun 24 15:01:18 2018  Check interval:           15552000 (6 months)  Next check after:         Fri Dec 21 15:01:18 2018  Lifetime writes:          10 MB  Reserved blocks uid:      0 (user root)  Reserved blocks gid:      0 (group root)  First inode:              11  Inode size:               256  Required extra isize:     28  Desired extra isize:      28  Journal inode:            8  Default directory hash:   half_md4  Directory Hash Seed:      89578f2c-49a6-4023-af1d-bd055875100f  Journal backup:           inode blocks  Journal features:         (none)  Journal size:             4096k  Journal length:           1024  Journal sequence:         0x00000001  Journal start:            0      Group 0: (Blocks 0-24319) [ITABLE_ZEROED]    Checksum 0xeec2, unused inodes 24309    Primary superblock at 0, Group descriptors at 1-1    Reserved GDT blocks at 2-6    Block bitmap at 7 (+7), Inode bitmap at 23 (+23)    Inode table at 39-1558 (+39)    21761 free blocks, 24309 free inodes, 2 directories, 24309 unused inodes    Free blocks: 2559-24319    Free inodes: 12-24320