在之前LVM分区无损增减 篇中有提到过LVM分区的无损增大和减小，不同的是，当是只是针对LVM下的ext分区的，在新版的RHEL7/centos7中默认使用的分区格式是xfs ，本篇就针对LVM下ext4和xfs分区的增大和缩小再唠叨下。
一、ext4分区下LVM的动态调整
在使用lvresize调整大小时结常需要注意与resize2fs执行的顺序。缩小空间时，一定要先执行resize2fs再执行lvresize；而增大时一定要先执行lvextend再执行resize2fs 。
1、减小大小
减小LVM分区时，一定要先umount掉挂载点再进行操作。
[root@361way.com ~]# df -H /mnt/
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-lvol0 805M 2.7M 760M 1% /mnt
[root@361way.com ~]# umount /mnt/
[root@361way.com ~]# resize2fs -f /dev/vg/lvol0 100M
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/vg/lvol0 to 102400 (1k) blocks.
The filesystem on /dev/vg/lvol0 is now 102400 blocks long.
[root@361way.com ~]# lvresize -L 100M /dev/vg/lvol0
WARNING: Reducing active logical volume to 100.00 MiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lvol0? [y/n]: y
Size of logical volume vg/lvol0 changed from 800.00 MiB (200 extents) to 100.00 MiB (25 extents).
Logical volume lvol0 successfully resized
[root@361way.com ~]# mount /dev/vg/lvol0 /mnt/
[root@361way.com ~]# df -H /mnt/
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-lvol0 94M 1.6M 87M 2% /mnt
[root@361way.com ~]#
2、增大空间
[root@361way.com ~]# lvextend -L 800M /dev/vg/lvol0
Size of logical volume vg/lvol0 changed from 100.00 MiB (25 extents) to 800.00 MiB (200 extents).
Logical volume lvol0 successfully resized
[root@361way.com ~]# resize2fs -f /dev/vg/lvol0
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg/lvol0 is mounted on /mnt; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 4
Performing an on-line resize of /dev/vg/lvol0 to 819200 (1k) blocks.
The filesystem on /dev/vg/lvol0 is now 819200 blocks long.
[root@361way.com ~]# df -H /mnt/
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-lvol0 805M 2.7M 761M 1% /mnt
3、一个命令搞定增大和减小
一会儿是增大，一会儿是减小，搞不好很容易搞错并造成分区损坏、数据受损，有没有不管增大减小一个命令全搞定的方法？当然有lvresize命令里有一个-r选项，该选项的作用是在执行lvresize命令的时候一并执行resize2fs ，强烈推荐该方法。
[root@361way.com ~]# df -H /mnt/
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-lvol0 805M 2.7M 761M 1% /mnt
[root@361way.com ~]# lvresize -L 300M -r /dev/vg/lvol0 -->注意此处的指定，增大时同样使用该指令
Do you want to unmount "/mnt"? [Y|n] y
fsck from util-linux-ng 2.17.2
/dev/mapper/vg-lvol0: 11/203200 files (0.0% non-contiguous), 36387/819200 blocks
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/mapper/vg-lvol0 to 307200 (1k) blocks.
The filesystem on /dev/mapper/vg-lvol0 is now 307200 blocks long.
Size of logical volume vg/lvol0 changed from 800.00 MiB (200 extents) to 300.00 MiB (75 extents).
Logical volume lvol0 successfully resized
[root@361way.com ~]#
[root@361way.com ~]# df -H /mnt/
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-lvol0 297M 2.2M 279M 1% /mnt
上面已经由800M 减小到了300M，而且更神奇的是，减小前我并没有umount分区，它自动提示让我们umount掉。此处使用同样的指令增大到500M 。
[root@361way.com ~]# lvresize -L 500M -r /dev/vg/lvol0
Size of logical volume vg/lvol0 changed from 300.00 MiB (75 extents) to 500.00 MiB (125 extents).
Logical volume lvol0 successfully resized
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/vg-lvol0 is mounted on /mnt; on-line resizing required
old desc_blocks = 2, new_desc_blocks = 2
Performing an on-line resize of /dev/mapper/vg-lvol0 to 512000 (1k) blocks.
The filesystem on /dev/mapper/vg-lvol0 is now 512000 blocks long.
[root@361way.com ~]# df -H /mnt/
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-lvol0 500M 2.4M 472M 1% /mnt
见证到奇迹了吧，就是这么任性。
二、XFS分区
xfs分区是不支持减小操作的，这点挺蛋疼。我们先当做不知道该特性，同lvresize -r 指定试下，结果如下：
# lvresize -L 50M /dev/vg2/xfstest -r
Phase 1 - find and verify superblock...
Phase 2 - using internal log
- scan filesystem freespace and inode maps...
- found root inode chunk
Phase 3 - for each AG...
- scan (but don't clear) agi unlinked lists...
- process known inodes and perform inode discovery...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- agno = 4
- process newly discovered inodes...
Phase 4 - check for duplicate blocks...
- setting up duplicate extent list...
- check for inodes claiming duplicate blocks...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- agno = 4
No modify flag set, skipping phase 5
Phase 6 - check inode connectivity...
- traversing filesystem ...
- traversal finished ...
- moving disconnected inodes to lost+found ...
Phase 7 - verify link counts...
No modify flag set, skipping filesystem flush and exiting.
fsadm: Xfs filesystem shrinking is unsupported -->看到相关信息了，不好意思，xfs不支持
fsadm failed: 1
Filesystem resize failed.
增大看下：
# df -Th /mnt
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg2-xfstest xfs 97M 5.3M 92M 6% /mnt
先使用lvextend增大LVM分区的大小
# lvextend -L 120M /dev/vg2/xfstest
Extending logical volume vo to 120.00 MiB
Logical volume vo successfully resized
再使用xfs_growfs在物理分区上调整
# xfs_growfs /dev/vg2/xfstest
meta-data=/dev/mapper/vg2-xfstest isize=256 agcount=5, agsize=5120 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=25600, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 25600 to 30720
# df -Th /mnt
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg2-xfstest xfs 117M 5.3M 92M 6% /mnt