Centos5.8 xen virtualization memory problems

Many servers in the data center perform xen virtualization. Suddenly, the memory size detected by free-M differs greatly from the actual memory size of the server .. I found a lot of information and compared several virtualized servers to find the kernel problems after virtualization.

* ***** If the actual memory of the server is less than or equal to 32 GB, after xen virtualization, the host memory plus the virtual machine memory is approximately equal to the actual physical memory, everything works.

* ******* If the physical memory of the server is greater than 32 GB (for example, 64 GB), the host can only recognize 32 GB at most.

The host memory plus the virtual machine memory is still smaller than the real server memory ..

The reason is found in the official documentation:

 

 

 

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The Red Hat Enterprise Linux kernel alization kernel does not support more than 32 GB of memory for x86_64 systems. if you need to boot the kernel alization Kernel on systems with more than 32 GB of physical memory installed, you must append the kernel command line with mem = 32G. this example shows how to enable the proper parameters in the grub. CONF file:

Red Hat Enterprise Linux virtual kernel does not support 32 GB storage on x86_64. If you need to install a physical memory larger than 32 GB to start the system's virtualization kernel, you must add the kernel command line:Mem = 32G. This example shows how to modify the appropriate parameters in the grub. conf file:

Grub. conf

Title Red Hat Enterprise Linux Server (2.6.18-4. elxen)
Root (hd0, 0)
Kernel/xen.gz-2.6.18-4-el5Mem = 32G
Module/vmlinuz-2.6.18-4. el5xen Ro root = label =/
Module/initrd-2.6.18-4.el5xen.img

* ******** This change method has not been implemented... Businesses are running on the server.

Http://www.centos.org/docs/5/html/Virtualization-en-US/ch-virt-hw-support.html (official address)

This article from the "Linux O & M beginner" blog, please be sure to retain this source http://ht712.blog.51cto.com/9397612/1568863

Centos5.8 xen virtualization memory problems