Linux下非逻辑卷扩容之创建逻辑卷pvcreate是否会损坏原数据测试

导语

添加硬盘

• 虚拟机添加一个5G的磁盘作为实验用
  
  
  

查看当前分区情况

lsblk

• 可以看到新加的5G磁盘sdb已经可以用了

[root@C8-196 ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 200G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 199G 0 part ├─cl-root 253:0 0 70G 0 lvm / ├─cl-swap 253:1 0 2G 0 lvm [SWAP] └─cl-home 253:2 0 127G 0 lvm /home sdb 8:16 0 5G 0 disk 

使用传统方式分区

fdisk /dev/sdb

• 创建一个主分区

[root@C8-196 ~]# fdisk /dev/sdb Welcome to fdisk (util-linux 2.32.1). 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. Created a new DOS disklabel with disk identifier 0x53b270c9. Command (m for help): n Partition type p primary (0 primary, 0 extended, 4 free) e extended (container for logical partitions) Select (default p): p Partition number (1-4, default 1): First sector (2048-, default 2048): Last sector, +sectors or +size{ 
   K,M,G,T,P} (2048-, default ): Created a new partition 1 of type 'Linux' and of size 5 GiB. Command (m for help): w The partition table has been altered. Calling ioctl() to re-read partition table. Syncing disks. 

• 再次查看分区情况，sdb被分成了一个主分区，TYPE为part，大小为5G

[root@C8-196 ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 200G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 199G 0 part ├─cl-root 253:0 0 70G 0 lvm / ├─cl-swap 253:1 0 2G 0 lvm [SWAP] └─cl-home 253:2 0 127G 0 lvm /home sdb 8:16 0 5G 0 disk └─sdb1 8:17 0 5G 0 part 

在新创建的分区上创建文件系统

• 使用xfs格式化sdb1

[root@C8-196 ~]# mkfs.xfs /dev/sdb1 meta-data=/dev/sdb1 isize=512 agcount=4, agsize= blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 data = bsize=4096 blocks=, 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 

创建挂载点并挂载新建分区

• 在根下创建目录data并挂载新分区到这个目录上

[root@C8-196 ~]# mkdir -v /data&& mount /dev/sdb1 /data&&df -Th mkdir: created directory '/data' Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 876M 0 876M 0% /dev tmpfs tmpfs 896M 0 896M 0% /dev/shm tmpfs tmpfs 896M 17M 879M 2% /run tmpfs tmpfs 896M 0 896M 0% /sys/fs/cgroup /dev/mapper/cl-root xfs 70G 2.3G 68G 4% / /dev/mapper/cl-home xfs 127G 939M 126G 1% /home /dev/sda1 xfs 1014M 197M 818M 20% /boot tmpfs tmpfs 180M 0 180M 0% /run/user/0 /dev/sdb1 xfs 5.0G 68M 5.0G 2% /data 

创建测试文件在新建磁盘分区上

• 写100个文件到磁盘上做数据测试
  for i in {1..100};do $(time dd if=/dev/zero of=/data/testw$i.db bs=4k count=10000);done&&ll /data&&df -Th
  
  

[root@C8-196 ~]# for i in {1..100};do $(time dd if=/dev/zero of=/data/testw$i.db bs=4k count=10000);done&&ll /data&&df -Th 10000+0 records in 10000+0 records out  bytes (41 MB, 39 MiB) copied, 0.0 s, 2.5 GB/s  中间的省略…… real 0m0.016s user 0m0.002s sys 0m0.014s 10000+0 records in 10000+0 records out  bytes (41 MB, 39 MiB) copied, 0.0 s, 2.7 GB/s real 0m0.017s user 0m0.001s sys 0m0.015s total   磁盘中已经有写入的文件了 -rw-r--r-- 1 root root  Mar 2 21:15 testw100.db -rw-r--r-- 1 root root  Mar 2 21:15 testw10.db -rw-r--r-- 1 root root  Mar 2 21:15 testw11.db  …… 中间的省略 -rw-r--r-- 1 root root  Mar 2 21:15 testw99.db -rw-r--r-- 1 root root  Mar 2 21:15 testw9.db  分区已经占了78%了 Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 876M 0 876M 0% /dev tmpfs tmpfs 896M 0 896M 0% /dev/shm tmpfs tmpfs 896M 17M 879M 2% /run tmpfs tmpfs 896M 0 896M 0% /sys/fs/cgroup /dev/mapper/cl-root xfs 70G 2.3G 68G 4% / /dev/mapper/cl-home xfs 127G 939M 126G 1% /home /dev/sda1 xfs 1014M 197M 818M 20% /boot tmpfs tmpfs 180M 0 180M 0% /run/user/0 /dev/sdb1 xfs 5.0G 3.9G 1.2G 78% /data 

直接对有数据的分区做pvcreate

• 很显然，处于安全考虑，已经mount的分区不能直接pvcreate

[root@C8-196 ~]#  [root@C8-196 ~]# type pvcreate  pvcreate is /usr/sbin/pvcreate [root@C8-196 ~]# pvcreate /dev/sdb1 Can't open /dev/sdb1 exclusively. Mounted filesystem? Can't open /dev/sdb1 exclusively. Mounted filesystem? 

umount以后再次pvcreate

• umount掉以后做pvcreate居然成功了，虽然提示了有xfs文件系统在分区上

[root@C8-196 ~]# umount /dev/sdb1 [root@C8-196 ~]# pvcreate /dev/sdb1 WARNING: xfs signature detected on /dev/sdb1 at offset 0. Wipe it? [y/n]: y Wiping xfs signature on /dev/sdb1. Physical volume "/dev/sdb1" successfully created. 

• 但是感觉pvcreate已经摧毁了已有的文件系统

创建逻辑卷

[root@C8-196 ~]# vgcreate vg_data /dev/sdb1 Volume group "vg_data" successfully created [root@C8-196 ~]# lvcreate -l 100%FREE -n data_lv vg_data Logical volume "data_lv" created. [root@C8-196 ~]# pvs&&vgs&&lvs PV VG Fmt Attr PSize PFree /dev/sda2 cl lvm2 a-- <199.00g 0 /dev/sdb1 vg_data lvm2 a-- <5.00g 0 VG #PV #LV #SN Attr VSize VFree cl 1 3 0 wz--n- <199.00g 0 vg_data 1 1 0 wz--n- <5.00g 0 LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert home cl -wi-ao---- 126.96g root cl -wi-ao---- 70.00g swap cl -wi-ao---- 2.03g data_lv vg_data -wi-a----- <5.00g 

再次尝试挂载/dev/sdb1

• 很显然已经挂载不上了

[root@C8-196 ~]# mount /dev/sdb1 /data mount: /data: unknown filesystem type 'LVM2_member'. 

尝试直接挂载新创建的lvm逻辑卷

• 很显然，没有文件系统是挂在不上的

[root@C8-196 ~]# ll /dev/mapper/vg_data-data_lv  lrwxrwxrwx 1 root root 7 Mar 2 21:28 /dev/mapper/vg_data-data_lv -> ../dm-3 [root@C8-196 ~]# ll /dev/vg_data/ total 0 lrwxrwxrwx 1 root root 7 Mar 2 21:28 data_lv -> ../dm-3 [root@C8-196 ~]# mount /dev/mapper/vg_data-data_lv /data mount: /data: wrong fs type, bad option, bad superblock on /dev/mapper/vg_data-data_lv, missing codepage or helper program, or other error. [root@C8-196 ~]# mount /dev/vg_data/data_lv /data mount: /data: wrong fs type, bad option, bad superblock on /dev/mapper/vg_data-data_lv, missing codepage or helper program, or other error. 

在新逻辑卷上创建文件系统

• 使用xfs格式化新创建的逻辑卷，格式化嘛，你懂的

[root@C8-196 ~]# mkfs.xfs /dev/mapper/vg_data-data_lv  meta-data=/dev/mapper/vg_data-data_lv isize=512 agcount=4, agsize= blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 data = bsize=4096 blocks=, 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 

挂载逻辑卷到曾经的data目录

mount /dev/mapper/vg_data-data_lv /data

[root@C8-196 ~]# mount /dev/mapper/vg_data-data_lv /data [root@C8-196 ~]# df -Th Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 876M 0 876M 0% /dev tmpfs tmpfs 896M 0 896M 0% /dev/shm tmpfs tmpfs 896M 17M 879M 2% /run tmpfs tmpfs 896M 0 896M 0% /sys/fs/cgroup /dev/mapper/cl-root xfs 70G 2.3G 68G 4% / /dev/mapper/cl-home xfs 127G 939M 126G 1% /home /dev/sda1 xfs 1014M 197M 818M 20% /boot tmpfs tmpfs 180M 0 180M 0% /run/user/0 /dev/mapper/vg_data-data_lv xfs 5.0G 68M 5.0G 2% /data 

查看目录下是否有文件

• 见证奇迹的时刻到了！

/dev/mapper/vg_data-data_lv xfs 5.0G 68M 5.0G 2% /data [root@C8-196 ~]# ll /data total 0 

• 很显然，毛线都没有了。
• 这目录下要是有生产数据，你就可以走人了！
• 又是一种删库跑路的新方法！

结论

• 使用pvcreate对已经挂载的分区不能直接创建pv
• 使用pvcreate对有数据且已解挂载的分区可以直接创建pv，会提示文件系统存在

使用pvcreate对有数据的分区创建pv会摧毁文件系统，文件就_无啦~

使用pvcreate对有数据的分区创建pv会摧毁文件系统，文件就_无啦~

使用pvcreate对有数据的分区创建pv会摧毁文件系统，文件就_无啦~