这一章节我们将来探讨下如何热添加虚拟磁盘，热扩容虚拟磁盘。热添加、热扩容意味着您可以这些操作可以在虚拟机保持运行的状态下执行，而不必关闭或者暂停虚拟机。KVM支持挂载物理磁盘或者虚拟磁盘。为了创建虚拟磁盘，我们可以使用qemu-img命令工具创建“qcow2”或者“img”格式的虚拟磁盘。当然使用强大的dd命令去创建一个非稀疏格式的的磁盘也是一个不错的选择。
为虚拟机挂载SAN/SCSI物理磁盘
- 为宿主机挂载物理磁盘“sdb”；
[root@test-kvm images]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 436K 0 rom
vda 253:0 0 20G 0 disk
└─vda1 253:1 0 20G 0 part /
sdb 253:16 0 1G 0 disk
- 查看vm当前磁盘映射关系；
[root@test-kvm images]# virsh list
Id Name State
----------------------------------------------------
1 generic running
4 centos7 running
[root@test-kvm images]# virsh domblklist centos7 --details
Type Device Target Source
------------------------------------------------
file disk vda /var/lib/libvirt/images/centos7.img
file cdrom hda -
- 将“sdb”挂载到虚拟机的“vdb”磁盘上；
[root@test-kvm images]# virsh attach-disk centos7 --source /dev/sdb --target vdb --persistent
Disk attached successfully
[root@test-kvm images]# virsh domblklist centos7 --details
Type Device Target Source
------------------------------------------------
file disk vda /var/lib/libvirt/images/centos7.img
block disk vdb /dev/sdb
file cdrom hda -
- 登录到虚拟机验证挂载情况;
[root@test-kvm images]# virsh console centos7
Connected to domain centos7
Escape character is ^]
CentOS Linux 7 (Core)
Kernel 3.10.0-514.el7.x86_64 on an x86_64
localhost login: root
Password:
Last login: Tue Jun 13 11:22:34 on ttyS0
[root@localhost ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 10G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 9G 0 part
├─cl-root 253:0 0 8G 0 lvm /
└─cl-swap 253:1 0 1G 0 lvm [SWAP]
vdb 252:16 0 1G 0 disk
创建并挂载虚拟磁盘：
- 创建虚拟磁盘，我们可以使用
qemu-img或dd命令创建虚拟磁盘。
_请留意我们在创建“qcow2”格式磁盘的时候使用了“preallocation＝metadata”选项，如果不适用预分配格式，挂载的虚拟磁盘将读取不到设置的大小_
[root@test-kvm images]# qemu-img create -f qcow2 -o preallocation=metadata centos7.disk1.qcow2 1G
Formatting 'centos7.disk1.qcow2', fmt=qcow2 size=1073741824 encryption=off cluster_size=65536 preallocation='metadata' lazy_refcounts=off
[root@test-kvm images]# qemu-img create -f raw centos7.disk2.img 256M
Formatting 'centos7.disk2.img', fmt=raw size=268435456
[root@test-kvm images]# dd if=/dev/zero of=centos7.disk3.img bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 0.792503 s, 1.3 GB/s
[root@test-kvm images]# ll centos7.disk*
-rw-r--r-- 1 root root 1074135040 Jun 13 13:57 centos7.disk1.qcow2
-rw-r--r-- 1 root root 268435456 Jun 13 13:57 centos7.disk2.img
-rw-r--r-- 1 root root 1048576000 Jun 13 13:58 centos7.disk3.img
- 挂载创建的虚拟磁盘；
[root@test-kvm images]# virsh attach-disk centos7 --source /var/lib/libvirt/images/centos7.disk1.qcow2 --target vdb --persistent
Disk attached successfully
[root@test-kvm images]# virsh attach-disk centos7 --source /var/lib/libvirt/images/centos7.disk2.img --target vdc --persistent
Disk attached successfully
[root@test-kvm images]# virsh attach-disk centos7 --source /var/lib/libvirt/images/centos7.disk3.img --target vdd --persistent
Disk attached successfully
热扩容虚拟磁盘
- 格式化、mount虚拟磁盘；
[root@localhost ~]# mkdir /storage
[root@localhost /]# mkfs.xfs /dev/vdb
meta-data=/dev/vdb isize=512 agcount=4, agsize=65560 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0, sparse=0
data = bsize=4096 blocks=262240, 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
[root@localhost /]# mount /dev/vdb /storage
[root@localhost /]# mount -v | grep storage
/dev/vdb on /storage type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
- 查看已挂载的虚拟磁盘信息，找到“vdb”的block id；
[root@test-kvm images]# virsh domblklist centos7 --details
Type Device Target Source
------------------------------------------------
file disk vda /var/lib/libvirt/images/centos7.img
file disk vdb /var/lib/libvirt/images/centos7.disk1.qcow2
file disk vdc /var/lib/libvirt/images/centos7.disk2.img
file disk vdd /var/lib/libvirt/images/centos7.disk3.img
[root@test-kvm images]# virsh pool-list
Name State Autostart
-------------------------------------------
default active yes
[root@test-kvm images]# virsh vol-list default
Name Path
------------------------------------------------------------------------------
CentOS-7-x86_64-Minimal-1611.iso /var/lib/libvirt/images/CentOS-7-x86_64-Minimal-1611.iso
centos7.disk1.qcow2 /var/lib/libvirt/images/centos7.disk1.qcow2
centos7.disk2.img /var/lib/libvirt/images/centos7.disk2.img
centos7.disk3.img /var/lib/libvirt/images/centos7.disk3.img
centos7.img /var/lib/libvirt/images/centos7.img
cirros-0.3.4-x86_64-disk.img /var/lib/libvirt/images/cirros-0.3.4-x86_64-disk.img
[root@test-kvm images]# virsh qemu-monitor-command centos7 --hmp "info block"
drive-virtio-disk0: removable=0 io-status=ok file=/var/lib/libvirt/images/centos7.img ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
drive-virtio-disk1: removable=0 io-status=ok file=/var/lib/libvirt/images/centos7.disk1.qcow2 ro=0 drv=raw encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
drive-virtio-disk2: removable=0 io-status=ok file=/var/lib/libvirt/images/centos7.disk2.img ro=0 drv=raw encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
drive-virtio-disk3: removable=0 io-status=ok file=/var/lib/libvirt/images/centos7.disk3.img ro=0 drv=raw encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
- 下面我们来为“vdb”扩容；
__注意不要减少虚拟磁盘的大小，这是不允许的，有可能会造成数据的丢失__
[root@test-kvm images]# virsh qemu-monitor-command centos7 --hmp "block_resize drive-virtio-disk1 2G"
- 现在虚拟磁盘的大小已经扩展到2G,但是要想使用这些扩容的容量，我们需要登录到虚拟机使用命令
xfs_growfs调整一下挂载文件的大小。
[root@test-kvm images]# virsh console centos7
Connected to domain centos7
Escape character is ^]
[root@localhost /]# lsblk | grep vdb
vdb 252:16 0 2G 0 disk /storage
[root@localhost /]# df -h /storage/
Filesystem Size Used Avail Use% Mounted on
/dev/vdb 1015M 33M 983M 4% /storage
[root@localhost /]# mount -v | grep storage
/dev/vdb on /storage type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
[root@localhost /]# xfs_growfs /storage/
meta-data=/dev/vdb isize=512 agcount=4, agsize=65560 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=262240, 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 262240 to 524288
[root@localhost /]# df -h /storage/
Filesystem Size Used Avail Use% Mounted on
/dev/vdb 2.0G 33M 2.0G 2% /storage
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