一、無需重啓主機增加磁盤
1、爲虛擬機添加多一塊磁盤
2、檢測磁盤空間
無法發現新增的2G磁盤
3、，重新掃描磁盤
通過重新掃描 SCSI （注：Small Computer System Interface 小型計算機系統接口）總線並添加 SCSI 設備，系統就可以擴展操作系統的物理卷磁盤空間，而且不需要重啓虛擬機。
[root@localhost ~]# ls /sys/class/scsi_host/
host0 host1 host2
[root@localhost ~]# echo "- - -" > /sys/class/scsi_host/host0/scan
[root@localhost ~]# echo "- - -" > /sys/class/scsi_host/host1/scan
[root@localhost ~]# echo "- - -" > /sys/class/scsi_host/host2/scan
使用下面的命令來檢查 SCSI 設備的名稱，然後重新掃描 SCSI 總線。
[root@localhost ~]# ls /sys/class/scsi_device/
0:0:0:0 0:0:1:0 2:0:0:0
[root@localhost ~]# echo 1>/sys/class/scsi_device/0\:0\:0\:0/device/rescan
[root@localhost ~]# echo 1>/sys/class/scsi_device/0\:0\:1\:0/device/rescan
[root@localhost ~]# echo 1>/sys/class/scsi_device/2\:0\:0\:0/device/rescan
二、擴容主機現有的根分區
如果磁盤使用率超過前期預算的，又需要保留所有數據，可以選擇擴容根分區
1、查看磁盤使用率和“/”目錄大小
[root@localhost ~]# df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos-root xfs 8.6G 1.1G 7.5G 13% /
devtmpfs devtmpfs 4.1G 0 4.1G 0% /dev
tmpfs tmpfs 4.2G 0 4.2G 0% /dev/shm
tmpfs tmpfs 4.2G 9.3M 4.1G 1% /run
tmpfs tmpfs 4.2G 0 4.2G 0% /sys/fs/cgroup
/dev/sda1 xfs 1.1G 153M 912M 15% /boot
tmpfs tmpfs 821M 0 821M 0% /run/user/0
2、爲新增的磁盤分區格式化
查看新的磁盤（是否存在/dev/sdb）
[root@localhost ~]# fdisk -l
Disk /dev/sda: 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: 0x00002170
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 20971519 9436160 8e Linux LVM
Disk /dev/mapper/centos-root: 8585 MB, 8585740288 bytes, 16769024 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 /dev/mapper/centos-swap: 1073 MB, 1073741824 bytes, 2097152 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 /dev/sdb: 2147 MB, 2147483648 bytes, 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
對磁盤進行分區
[root@localhost ~]# fdisk /dev/sdb
fdisk的交互模式，依次輸入
n --創建新分區
p --創建主分區
<回車> --默認分區編號
<回車> --默認起始扇區位置。
<回車> --默認結束扇區位置。
w --寫入分區表
3、再查看磁盤能看到新增的/dev/sdb1
[root@localhost ~]# fdisk -l
......
Disk /dev/sdb: 2147 MB, 2147483648 bytes, 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 label type: dos
Disk identifier: 0x07276705
Device Boot Start End Blocks Id System
/dev/sdb1 2048 4194303 2096128 83 Linux
4、將新磁盤分區擴容到根分區 "/"
4.1、查看卷分組
[root@localhost ~]# vgdisplay -v
--- 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 <9.00 GiB
PE Size 4.00 MiB
Total PE 2303
Alloc PE / Size 2303 / <9.00 GiB
Free PE / Size 0 / 0
VG UUID DmqyXY-Kj13-sfSR-v9i5-wpLc-ht7c-kPJIvC
......
--- Physical volumes ---
PV Name /dev/sda2
PV UUID 7CPA1z-xrMe-CAo7-g14k-cL8B-zgm2-vXbuP3
PV Status allocatable
Total PE / Free PE 2303 / 0
4.2、爲新增的分區創建物理卷
[root@localhost ~]# pvcreate /dev/sdb1
Physical volume "/dev/sdb1" successfully created.
查看創建結果，有新建的/dev/sdb1，大小爲2G
[root@localhost ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name centos
PV Size <9.00 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 2303
Free PE 0
Allocated PE 2303
PV UUID 7CPA1z-xrMe-CAo7-g14k-cL8B-zgm2-vXbuP3
"/dev/sdb1" is a new physical volume of "<2.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb1
VG Name
PV Size <2.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID SnXl2W-LsFp-FHUT-M4Ze-yZy9-Y6WH-p3kQ0S
4.3、擴展卷分組，“centos”就是前面使用vgdisplay查看到的主機原本的卷分組名
[root@localhost ~]# vgextend centos /dev/sdb1
Volume group "centos" successfully extended
4.4、查看邏輯卷，並擴展邏輯卷
目前/dev/centos/root的LV Size大小爲8G
[root@localhost ~]# lvdisplay
--- Logical volume ---
LV Path /dev/centos/swap
LV Name swap
VG Name centos
LV UUID 4U7aBO-Nknq-ZkLc-sLXU-bGpH-Ru9B-5lzejQ
LV Write Access read/write
LV Creation host, time localhost, 2020-05-08 02:15:24 -0400
LV Status available
# open 2
LV Size 1.00 GiB
Current LE 256
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:1
--- Logical volume ---
LV Path /dev/centos/root
LV Name root
VG Name centos
LV UUID D20gW5-4CiO-Pdfp-68yn-t4wG-h1cs-aw4ge7
LV Write Access read/write
LV Creation host, time localhost, 2020-05-08 02:15:26 -0400
LV Status available
# open 1
LV Size <8.00 GiB
Current LE 2047
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
擴展操作
[root@localhost ~]# lvextend -L +1G /dev/centos/root
Size of logical volume centos/root changed from <8.00 GiB (2047 extents) to <9.00 GiB (2303 extents).
Logical volume centos/root successfully resized.
注意：不能全部把2G空間都擴展，因爲實際沒有這麼大的空間
報錯如下，提只有511可用
[root@localhost ~]# lvextend -L +2G /dev/centos/root
Insufficient free space: 512 extents needed, but only 511 available
執行pvdisplay可以看到可用的PE數量是511,而且每個PE大小是4.00MiB，所以實際空間並沒有2G
[root@localhost ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name centos
PV Size <9.00 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 2303
Free PE 0
Allocated PE 2303
PV UUID 7CPA1z-xrMe-CAo7-g14k-cL8B-zgm2-vXbuP3
--- Physical volume ---
PV Name /dev/sdb1
VG Name centos
PV Size <2.00 GiB / not usable 3.00 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 511
Free PE 511
Allocated PE 0
PV UUID SnXl2W-LsFp-FHUT-M4Ze-yZy9-Y6WH-p3kQ0S
4.5、因爲安裝CentOS用的xfs分區，所以使用命令xfs_growfs擴展文件系統大小。
[root@localhost ~]# xfs_growfs /dev/centos/root
meta-data=/dev/mapper/centos-root isize=512 agcount=4, agsize=524032 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=2096128, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 2096128 to 2358272
5、再次查看根目錄大小，/dev/mapper/centos-root已經擴容到9G
[root@localhost ~]# df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/centos-root xfs 9.7G 1.1G 8.6G 12% /
devtmpfs devtmpfs 4.1G 0 4.1G 0% /dev
tmpfs tmpfs 4.2G 0 4.2G 0% /dev/shm
tmpfs tmpfs 4.2G 9.3M 4.1G 1% /run
tmpfs tmpfs 4.2G 0 4.2G 0% /sys/fs/cgroup
/dev/sda1 xfs 1.1G 153M 912M 15% /boot
tmpfs tmpfs 821M 0 821M 0% /run/user/0
三、爲主機掛載新的磁盤空間
不改變原主機磁盤狀態，新掛載一個磁盤做數據存儲
1、一樣先看是否能看到新添加的磁盤，不能就執行第一大點的操作
[root@localhost ~]# fdisk -l
......
Disk /dev/sdb: 2147 MB, 2147483648 bytes, 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
2、對新磁盤進行分區
再查看磁盤個數與分區情況
[root@localhost ~]# fdisk -l
......
Disk /dev/sdb: 2147 MB, 2147483648 bytes, 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 label type: dos
Disk identifier: 0xaaed78bd
Device Boot Start End Blocks Id System
/dev/sdb1 2048 4194303 2096128 83 Linux
3、格式化
[root@localhost ~]# partprobe /dev/sdb
[root@localhost ~]# mkfs.ext3 /dev/sdb1
4、創建掛載目錄
[root@localhost ~]# mkdir /mydata
5、掛載分區
[root@localhost ~]# mount /dev/sdb1 /mydata
6、創建開機自動掛載
7、查看掛載
8、也可以通過磁盤的UUID進行掛載
查看uuid
[root@localhost ~]# blkid
8、掛載
9、重啓，再查看掛載
