DAY04 - 第七章：磁盘阵列 - 《《Linux就该这么学》读后感》

1、RAID
2、LVM
- 2.1 部署逻辑卷
2.2 扩容逻辑卷
2.3 缩小逻辑卷
2.4 逻辑卷快照（没研究懂是干嘛的）
2.5 删除逻辑卷

1、RAID

1.1、阵列分析

目前常用的 RAID 磁盘阵列的方案有四种：RAID0、RAID1、RAID5、RAID10

阵列技术	作用	优势	劣势
RAID0	两块盘合为一块	提升硬盘数据的吞吐速度	数据不安全，某一块盘换了就读取不了
RAID1	一比一复制	数据安全	磁盘利用率只有50%
RAID5	把硬盘设备的数据奇偶校验信息保存到其他硬盘设备中	0和1的折中结合体，既能提高吞吐速度又能做到数据安全保障	提供数据安全保障，但保障程度要比 RAID1 低，磁盘空间利用率要比RAID1高
RAID10	RAID0和RAID1的结合体，先分别两两制作成 RAID 1 磁盘阵列，再对两个 RAID 1 磁盘阵列实施 RAID 0 技术	完美解决数据吞吐速度和安全问题	成本高，比较费盘

1.2、磁盘阵列的部署

mdadm 命令用于管理 Linux 系统中的软件 RAID 硬盘阵列
参数：
    -a   检测设备名称
    -n   指定设备数量
    -l   指定 RAID 级别
    -C   创建
    -v   显示过程
    -f   模拟设备损坏
    -r   移除设备
    -Q   查看摘要信息
    -D   查看详细信息
    -S   停止 RAID 磁盘阵列

创建RAID10阵列

1、将虚拟机上增加4块硬盘

2、将增加的盘创建分区


[root@localhost ~]# fdisk  /dev/sdc
欢迎使用 fdisk (util-linux 2.23.2)。
更改将停留在内存中，直到您决定将更改写入磁盘。
使用写入命令前请三思。
Device does not contain a recognized partition table
使用磁盘标识符 0xdac4b323 创建新的 DOS 磁盘标签。
命令(输入 m 获取帮助)：n    #创建分区
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p      #创建主分区
分区号 (1-4，默认 1)：
起始 扇区 (2048-10485759，默认为 2048)：
将使用默认值 2048
Last 扇区, +扇区 or +size{K,M,G} (2048-10485759，默认为 10485759)：5G
值超出范围。
Last 扇区, +扇区 or +size{K,M,G} (2048-10485759，默认为 10485759)：
将使用默认值 10485759
分区 1 已设置为 Linux 类型，大小设为 5 GiB
命令(输入 m 获取帮助)：w
The partition table has been altered!
Calling ioctl() to re-read partition table.
正在同步磁盘。

3、创建RAID区

[root@localhost ~]# mdadm -Cv /dev/md0 -a yes -l 10 -n 4 /dev/sdc /dev/sdd /dev/sde /dev/sdf
mdadm: layout defaults to n2
mdadm: layout defaults to n2
mdadm: chunk size defaults to 512K
mdadm: /dev/sdc appears to be part of a raid array:
       level=raid10 devices=4 ctime=Thu Apr 28 13:50:25 2022
mdadm: partition table exists on /dev/sdc but will be lost or
       meaningless after creating array
mdadm: /dev/sdd appears to be part of a raid array:
       level=raid10 devices=4 ctime=Thu Apr 28 13:50:25 2022
mdadm: partition table exists on /dev/sdd but will be lost or
       meaningless after creating array
mdadm: /dev/sde appears to be part of a raid array:
       level=raid10 devices=4 ctime=Thu Apr 28 13:50:25 2022
mdadm: partition table exists on /dev/sde but will be lost or
       meaningless after creating array
mdadm: /dev/sdf appears to be part of a raid array:
       level=raid10 devices=4 ctime=Thu Apr 28 13:50:25 2022
mdadm: partition table exists on /dev/sdf but will be lost or
       meaningless after creating array
mdadm: size set to 5237760K
Continue creating array? 
Continue creating array? (y/n) y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.

4、挂载RAID区


[root@localhost ~]#  mkfs.ext4 /dev/md0
mke2fs 1.42.9 (28-Dec-2013)
文件系统标签=
OS type: Linux
块大小=4096 (log=2)
分块大小=4096 (log=2)
Stride=128 blocks, Stripe width=256 blocks
655360 inodes, 2618880 blocks
130944 blocks (5.00%) reserved for the super user
第一个数据块=0
Maximum filesystem blocks=2151677952
80 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
Allocating group tables: 完成                            
正在写入inode表: 完成                            
Creating journal (32768 blocks): 完成
Writing superblocks and filesystem accounting information: 完成 
[root@localhost ~]# mount /dev/md0 /RAID/
[root@localhost ~]# df -TH
/dev/md0                ext4       11G   38M  9.9G    1% /RAID

5、永久挂载

5、永久挂载
[root@localhost ~]# vi /etc/fstab 
/dev/mapper/centos-root /                         xfs     defaults        0 0
UUID=41ff41fd-8e69-450d-9ebb-7551b9a76153 /boot   xfs     defaults        0 0
/dev/mapper/centos-swap swap                      swap    defaults        0 0
/dev/sdb1                                 /nesFs  xfs     defaults        0 0     
/dev/md0                                  /RAID   ext4    defaults        0 0

6、查看阵列信息

[root@localhost ~]# mdadm -D
mdadm: No devices given.
[root@localhost ~]# mdadm -D /dev/md0 
/dev/md0:
           Version : 1.2
     Creation Time : Thu Apr 28 14:06:40 2022
        Raid Level : raid10
        Array Size : 10475520 (9.99 GiB 10.73 GB)
     Used Dev Size : 5237760 (5.00 GiB 5.36 GB)
      Raid Devices : 4
     Total Devices : 4
       Persistence : Superblock is persistent
       Update Time : Thu Apr 28 14:08:34 2022
             State : clean 
    Active Devices : 4
   Working Devices : 4
    Failed Devices : 0
     Spare Devices : 0
            Layout : near=2
        Chunk Size : 512K
Consistency Policy : resync
              Name : localhost.localdomain:0  (local to host localhost.localdomain)
              UUID : 4aeb4a9c:b44cddab:f8595c65:ebdc5a0e
            Events : 19
    Number   Major   Minor   RaidDevice State
       0       8       32        0      active sync set-A   /dev/sdc
       1       8       48        1      active sync set-B   /dev/sdd
       2       8       64        2      active sync set-A   /dev/sde
       3       8       80        3      active sync set-B   /dev/sdf

7、移除阵列

[root@localhost ~]# mdadm -S /dev/md0 
mdadm: stopped /dev/md0
[root@localhost ~]# mdadm -D    #再次查看阵列就没有了
mdadm: No devices given.

1.3、修复阵列

在RAID10级别的磁盘阵列中,当RAID1磁盘阵列中存在一个故障盘时并不影响RAID10磁盘阵列的使用。当购买了新的硬盘设备后再使用mdadm命令来予以替换即可，在此期间我们可以在/RAID 目录中正常地创建或删除文件。由于我们是在虚拟机中模拟硬盘，所以先重启。再把新的硬盘添加到 RAID 磁盘阵列中

1、模拟损坏/dev/sdc盘损坏

[root@localhost ~]#  mdadm /dev/md0 -f /dev/sdc
mdadm: set /dev/sdc faulty in /dev/md0
[root@localhost ~]# 
[root@localhost ~]# 
[root@localhost ~]# 
[root@localhost ~]# mdadm -D
mdadm: No devices given.
[root@localhost ~]# mdadm -D /dev/md0 
/dev/md0:
           Version : 1.2
     Creation Time : Thu Apr 28 14:06:40 2022
        Raid Level : raid10
        Array Size : 10475520 (9.99 GiB 10.73 GB)
     Used Dev Size : 5237760 (5.00 GiB 5.36 GB)
      Raid Devices : 4
     Total Devices : 4
       Persistence : Superblock is persistent
       Update Time : Thu Apr 28 14:22:56 2022
             State : clean, degraded 
    Active Devices : 3
   Working Devices : 3
    Failed Devices : 1
     Spare Devices : 0
            Layout : near=2
        Chunk Size : 512K
Consistency Policy : resync
              Name : localhost.localdomain:0  (local to host localhost.localdomain)
              UUID : 4aeb4a9c:b44cddab:f8595c65:ebdc5a0e
            Events : 21
    Number   Major   Minor   RaidDevice State
       -       0        0        0      removed
       1       8       48        1      active sync set-B   /dev/sdd
       2       8       64        2      active sync set-A   /dev/sde
       3       8       80        3      active sync set-B   /dev/sdf
       0       8       32        -      faulty   /dev/sdc
[root@localhost ~]#

2、重新分区挂载

 mdadm /dev/md0 -a /dev/sdb
 [root@localhost ~]# mdadm -D /dev/md0 
/dev/md0:
           Version : 1.2
     Creation Time : Thu Apr 28 14:06:40 2022
        Raid Level : raid10
        Array Size : 10475520 (9.99 GiB 10.73 GB)
     Used Dev Size : 5237760 (5.00 GiB 5.36 GB)
      Raid Devices : 4
     Total Devices : 4
       Persistence : Superblock is persistent
       Update Time : Thu Apr 28 14:39:06 2022
             State : clean 
    Active Devices : 4
   Working Devices : 4
    Failed Devices : 0
     Spare Devices : 0
            Layout : near=2
        Chunk Size : 512K
Consistency Policy : resync
              Name : localhost.localdomain:0  (local to host localhost.localdomain)
              UUID : 4aeb4a9c:b44cddab:f8595c65:ebdc5a0e
            Events : 44
    Number   Major   Minor   RaidDevice State
       4       8       32        0      active sync set-A   /dev/sdc
       1       8       48        1      active sync set-B   /dev/sdd
       2       8       64        2      active sync set-A   /dev/sde
       3       8       80        3      active sync set-B   /dev/sdf
[root@localhost ~]#

2、LVM

LVM常用的命令，参数

2.1 部署逻辑卷

1、支持LVM 技术

#让两块新增的盘支持LVM技术
[root@localhost ~]# pvcreate /dev/sdg /dev/sdh 
  Physical volume "/dev/sdg" successfully created.
  Physical volume "/dev/sdh" successfully created.

2、把硬盘设备加入到 storage 卷组

[root@localhost ~]# vgcreate storage /dev/sdg /dev/sdh
  Volume group "storage" successfully created
[root@localhost ~]# vgdisplay
  --- Volume group ---
  VG Name               centos
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <19.00 GiB
  PE Size               4.00 MiB
  Total PE              4863
  Alloc PE / Size       4863 / <19.00 GiB
  Free  PE / Size       0 / 0   
  VG UUID               qRB4Xz-Z6BH-NNJz-yKdB-dkyB-3N1W-Vyko4D
  --- Volume group ---
  VG Name               storage
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               9.99 GiB
  PE Size               4.00 MiB
  Total PE              2558
  Alloc PE / Size       0 / 0   
  Free  PE / Size       2558 / 9.99 GiB
  VG UUID               gJACUj-0EUM-Ji8B-0quN-8cgC-Md7y-xlnHGu
[root@localhost ~]#

3、切割逻辑卷

这里需要注意切割单位的问题。在对逻辑卷进行切割时有两种计量单位。第一种是以容
量为单位，所使用的参数为-L。例如，使用-L 150M 生成一个大小为 150MB 的逻辑卷。另外
一种是以基本单元的个数为单位，所使用的参数为-l。每个基本单元的大小默认为 4MB。例
如，使用-l 37 可以生成一个大小为 37×4MB=148MB 的逻辑卷

#方式一切割
[root@localhost ~]# lvcreate -L 150M storage
  Rounding up size to full physical extent 152.00 MiB
  Logical volume "lvol0" created.
[root@localhost ~]# 
#方式二切割
[root@localhost ~]# lvcreate -n vo -l 37 storage
  Logical volume "vo" created.
[root@localhost ~]# lvcreate -L 150M storage  #显示逻辑卷
 --- Logical volume ---
  LV Path                /dev/storage/lvol0
  LV Name                lvol0
  VG Name                storage
  LV UUID                71Avnv-XsAg-1faG-cQqB-ViSM-uUuF-bW9ZMs
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2022-04-28 16:44:13 +0800
  LV Status              available
  # open                 0
  LV Size                152.00 MiB
  Current LE             38
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2
  --- Logical volume ---
  LV Path                /dev/storage/vo
  LV Name                vo
  VG Name                storage
  LV UUID                S2pXqR-2WVH-sAFA-0Gdn-Rhj8-NFsb-2dZ7N5
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2022-04-28 16:45:22 +0800
  LV Status              available
  # open                 0
  LV Size                148.00 MiB
  Current LE             37
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:3

4、将逻辑卷格式化，挂载使用

[root@localhost ~] mkfs.ext4   /dev/storage/lvol0  #格式化为ext4格式
mke2fs 1.42.9 (28-Dec-2013)
文件系统标签=
OS type: Linux
块大小=1024 (log=0)
分块大小=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
38912 inodes, 155648 blocks
7782 blocks (5.00%) reserved for the super user
第一个数据块=1
Maximum filesystem blocks=33816576
19 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks: 
    8193, 24577, 40961, 57345, 73729
Allocating group tables: 完成                            
正在写入inode表: 完成                            
Creating journal (4096 blocks): 完成
Writing superblocks and filesystem accounting information: 完成 
[root@localhost data]# mount /dev/storage/vo /data/a
[root@localhost data]# mount /dev/storage/lvol0 /data/b/
[root@localhost data]# df -Th 
/dev/mapper/storage-vo    ext4      140M  1.6M  128M    2% /data/a
/dev/mapper/storage-lvol0 ext4      144M  1.6M  132M    2% /data/b

5、永久写入

echo "/dev/mapper/storage-vo /data/a ext4 defaults 0 0"  >>/etc/fstab
echo "/dev/mapper/storage-lvol0 /data/b ext4 defaults 0 0"  >>/etc/fstab

2.2 扩容逻辑卷

1、扩容

[root@localhost vo]#  lvextend -L 290M /dev/storage/vo
  Rounding size to boundary between physical extents: 292.00 MiB.
  Size of logical volume storage/vo changed from 148.00 MiB (37 extents) to 292.00 MiB (73 extents).
  Logical volume storage/vo successfully resized.

2、检查硬盘完整性，并重置硬盘容量。

[root@localhost vo]# e2fsck -f /dev/storage/vo   #可不做
e2fsck 1.42.9 (28-Dec-2013)
/dev/storage/vo is mounted.
e2fsck: 无法继续, 中止.
[root@localhost vo]# resize2fs /dev/storage/vo 
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/storage/vo is mounted on /data/vo; on-line resizing required
old_desc_blocks = 2, new_desc_blocks = 3
The filesystem on /dev/storage/vo is now 299008 blocks long.

3、查看容量

[root@localhost vo]# mount -a    #重新挂载  可不做
[root@localhost vo]# df -TH
/dev/mapper/storage-vo    ext4      293M  2.2M  274M    1% /data/vo

2.3 缩小逻辑卷

相较于扩容逻辑卷，在对逻辑卷进行缩容操作时，其丢失数据的风险更大。所以在生产环境中执行相应操作时，一定要提前备份好数据。在执行缩容操作前记得先把文件系统卸载掉。

1、检查文件的完整性

[root@localhost lvol0]# umount /data/vo/  #先取消挂载
[root@localhost lvol0]#  e2fsck -f /dev/storage/vo
e2fsck 1.42.9 (28-Dec-2013)
第一步: 检查inode,块,和大小
第二步: 检查目录结构
第3步: 检查目录连接性
Pass 4: Checking reference counts
第5步: 检查簇概要信息
/dev/storage/vo: 12/74000 files (0.0% non-contiguous), 15509/299008 blocks

2、缩小

[root@localhost lvol0]# resize2fs /dev/storage/vo 100M
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/storage/vo to 102400 (1k) blocks.
The filesystem on /dev/storage/vo is now 102400 blocks long.
[root@localhost lvol0]# lvreduce -L 100M /dev/storage/vo
  WARNING: Reducing active logical volume to 100.00 MiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce storage/vo? [y/n]: y
  Size of logical volume storage/vo changed from 292.00 MiB (73 extents) to 100.00 MiB (25 extents).
  Logical volume storage/vo successfully resized.

3、挂载查看大小

[root@localhost lvol0]# mount /dev/storage/vo /data/vo/
[root@localhost lvol0]# df -Th
/dev/mapper/storage-vo    ext4       93M  1.6M   85M    2% /data/vo

2.4 逻辑卷快照（没研究懂是干嘛的）

LVM 还具备有“快照卷”功能，该功能类似于虚拟机软件的还原时间点功能。例如，可
以对某一个逻辑卷设备做一次快照，如果日后发现数据被改错了，就可以利用之前做好的快
照卷进行覆盖还原。
LVM 的快照卷功能有两个特点：
第一个就是：快照卷的容量必须等同于逻辑卷的容量
第二个就是：快照卷仅一次有效，一旦执行还原操作后则会被立即自动删除。

1、生成快照卷

#先查看卷组的信息
[root@localhost vo]# vgdisplay 
[root@localhost data]# lvcreate -L 100M -s -n SNAP /dev/storage/vo 
  Logical volume "SNAP" created.
[root@localhost data]# lvdisplay

2、查看效果

再向逻辑卷中添加文件之前使用lvdisplai查看分配给快照的空间是
Allocated to snapshot  0.01%
再向逻辑卷中添加文件后再使用lvsidplay查看分配给快照空间
Allocated to snapshot  5.45%

3、使用功能

[root@localhost dev]# umount /data/vo/
[root@localhost dev]#  lvconvert --merge /dev/storage/SNAP
  Merging of volume storage/SNAP started.
  storage/vo: Merged: 100.00%
[root@localhost dev]# mount /dev/storage/vo /data/vo/

4、检查快照

[root@localhost dev]#  lvdisplay  #发现之前的快照卷没有了

2.5 删除逻辑卷

1、取消挂载

[root@localhost vo]# umount  /data/vo
vi /etc/fstab   #将之前永久挂载的配置删除

2、删除逻辑卷

[root@localhost vo]#  lvremove /dev/storage/vo
Do you really want to remove active logical volume vo? [y/n]: y
 Logical volume "vo" successfully removed

3、删除卷组

[root@localhost vo]# vgremove storage
 Volume group "storage" successfully removed

4、删除物理卷设备

[root@localhost vo]#pvremove /dev/sdg /dev/sdh
 Labels on physical volume "/dev/sdg" successfully wiped 
 Labels on physical volume "/dev/sdh" successfully wiped