KVM的热添加技术之内存

目录

一.调小虚拟机内存配置案例

1.查看虚拟机现有的内存配置

[root@yinzhengjie-kvm189 ~]# virsh list
 Id    Name                           State
----------------------------------------------------
 2     yinzhengjie-kvm01              running

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh edit yinzhengjie-kvm01 
<domain type='kvm'>
  ...(很明显，我的虚拟机内存应该只有2GB)
  <memory unit='KiB'>2097152</memory>
  <currentMemory unit='KiB'>2097152</currentMemory>
  ...

2.验证虚拟机内存大小

[root@yinzhengjie-kvm189 ~]# virsh list
 Id    Name                           State
----------------------------------------------------
 2     yinzhengjie-kvm01              running

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh console yinzhengjie-kvm01 
Connected to domain yinzhengjie-kvm01
Escape character is ^]

[root@yinzhengjie-kvm01 ~]# free 
              total        used        free      shared  buff/cache   available
Mem:        2046820      178792     1730784       41460      137244     1703180
Swap:             0           0           0
[root@yinzhengjie-kvm01 ~]# 
[root@yinzhengjie-kvm01 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           2.0G        174M        1.7G         40M        134M        1.6G
Swap:            0B          0B          0B
[root@yinzhengjie-kvm01 ~]#

3.调整虚拟机的内存

[root@yinzhengjie-kvm189 ~]# virsh list
 Id    Name                           State
----------------------------------------------------
 2     yinzhengjie-kvm01              running

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh dumpxml yinzhengjie-kvm01 | egrep "memory|currentMemory"
  <memory unit='KiB'>2097152</memory>
  <currentMemory unit='KiB'>2097152</currentMemory>
[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh setmem yinzhengjie-kvm01 4096M
error: invalid argument: cannot set memory higher than max memory

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh setmem yinzhengjie-kvm01 1024M

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh dumpxml yinzhengjie-kvm01 | egrep "memory|currentMemory"
  <memory unit='KiB'>2097152</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
[root@yinzhengjie-kvm189 ~]#

4.调整虚拟机内存后进行验证

[root@yinzhengjie-kvm189 ~]# virsh list
 Id    Name                           State
----------------------------------------------------
 2     yinzhengjie-kvm01              running

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh console yinzhengjie-kvm01 
Connected to domain yinzhengjie-kvm01
Escape character is ^]

[root@yinzhengjie-kvm01 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           974M        174M        666M         40M        134M        639M
Swap:            0B          0B          0B
[root@yinzhengjie-kvm01 ~]# 
[root@yinzhengjie-kvm01 ~]# free 
              total        used        free      shared  buff/cache   available
Mem:         998244      178264      682760       41460      137220      655148
Swap:             0           0           0
[root@yinzhengjie-kvm01 ~]#

二.调大虚拟机内存配置案例

1.手动方式修改虚拟机内存配置

[root@yinzhengjie-kvm189 ~]# virsh list --all
 Id    Name                           State
----------------------------------------------------
 2     yinzhengjie-kvm01              running

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh destroy yinzhengjie-kvm01 
Domain yinzhengjie-kvm01 destroyed

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh list --all
 Id    Name                           State
----------------------------------------------------
 -     yinzhengjie-kvm01              shut off

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh edit yinzhengjie-kvm01 
<domain type='kvm'>
  <name>yinzhengjie-kvm01</name>
  ...
  <memory unit='MiB'>4096</memory>
  <currentMemory unit='KiB'>2097152</currentMemory>
  ...
  
  
温馨提示:
	修改后，重新打开虚拟机，你会发现虚拟机的内存限制的单位依旧是KB哟~

2.基于命令行方式修改虚拟机内存配置

[root@yinzhengjie-kvm189 ~]# virsh list --all
 Id    Name                           State
----------------------------------------------------
 -     yinzhengjie-kvm01              shut off

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh setmaxmem yinzhengjie-kvm01 8192M

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh edit yinzhengjie-kvm01 
<domain type='kvm'>
  <name>yinzhengjie-kvm01</name>
  ...
  <memory unit='KiB'>8388608</memory>
  <currentMemory unit='KiB'>2097152</currentMemory>
...

3.手动修改虚拟机内存上限

	1.修改内存前查看虚拟机状态
[root@yinzhengjie-kvm189 ~]# virsh list --all
 Id    Name                           State
----------------------------------------------------
 -     yinzhengjie-kvm01              shut off

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh start yinzhengjie-kvm01 
Domain yinzhengjie-kvm01 started

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh console yinzhengjie-kvm01 
Connected to domain yinzhengjie-kvm01
Escape character is ^]

CentOS Linux 7 (Core)
Kernel 3.10.0-1160.el7.x86_64 on an x86_64

yinzhengjie-kvm01 login: root
Password: 
Last login: Wed Apr 10 17:55:50 on ttyS0
[root@yinzhengjie-kvm01 ~]# 
[root@yinzhengjie-kvm01 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           1.8G        332M        1.4G        8.5M         97M        1.3G
Swap:            0B          0B          0B
[root@yinzhengjie-kvm01 ~]# 


	2.修改内存上限为4GB
[root@yinzhengjie-kvm189 ~]# virsh setmem yinzhengjie-kvm01 4096M

[root@yinzhengjie-kvm189 ~]# 
[root@yinzhengjie-kvm189 ~]# virsh console yinzhengjie-kvm01 
Connected to domain yinzhengjie-kvm01
Escape character is ^]

[root@yinzhengjie-kvm01 ~]# 
[root@yinzhengjie-kvm01 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           3.8G        330M        3.4G        8.5M         97M        3.3G
Swap:            0B          0B          0B
[root@yinzhengjie-kvm01 ~]#

三.其他注意事项

1.内存的永久配置

修改当前内存的两种方式:
	- 临时配置
virsh setmem yinzhengjie-kvm01 4096M

	- 永久配置
virsh setmem yinzhengjie-kvm01 4096M --config



修改内存上限的两种方式:
	- 临时配置
virsh setmaxmem yinzhengjie-kvm01 8192M

	- 永久配置
virsh setmaxmem yinzhengjie-kvm01 8192M --config

2.创建虚拟机时指定内存上限

	1.只指定“--memory”参数时，默认是2GB
virt-install --virt-type kvm \
    --os-type=linux \
    --os-variant rhel7 \
    --name yinzhengjie-kvm01 \
    --memory 2048 \
    --vcpus 2 \
    --disk /opt/yinzhengjie-kvm01.raw,format=raw,size=10 \
    --cdrom /opt/CentOS-7-x86_64-DVD-2009.iso \
    --network  network=default \
    --graphics vnc,listen=0.0.0.0 \
    --noautoconsole
    
    
    2.使用"--maxmemory"指定最大的内存上限
virt-install --virt-type kvm \
    --os-type=linux \
    --os-variant rhel7 \
    --name yinzhengjie-kvm01 \
    --memory 2048,--maxmemory=2048 \
    --vcpus 2 \
    --disk /opt/yinzhengjie-kvm01.raw,format=raw,size=10 \
    --cdrom /opt/CentOS-7-x86_64-DVD-2009.iso \
    --network  network=default \
    --graphics vnc,listen=0.0.0.0 \
    --noautoconsole

3.其他注意事项

- 创建虚拟机时，虚拟机的最大内存不能超过该虚拟机所在宿主机的最大内存。
	举个例子: 
		目前有2台128GB内存的主机，那么能够实现创建一个256GB内存的虚拟机呢？答案是否定的。
		虚拟机最大的内存应该小于128GB，因为宿主机的操作系统也是要占用一定内存的。
		若真能实现，就不会淘汰旧的机器了，而且就算基于网络实现了该功能，那么性能估计会巨差且稳定性不高。
		因为CPU的频率是GB赫兹，而网卡的传输速度万兆速度，完全不在一个维度。
		
- 在云平台购买虚拟机的时候，都会有最高限制，这是因为创建的虚拟机不得超过该虚拟机所在宿主机的总内存。
posted @ 2024-04-10 00:04  尹正杰  阅读(4)  评论(0)  编辑  收藏  举报