Thursday, October 09, 2008

F10-beta VM Memory Management

Sadness. Gone is the ability to dynamically change the memory allocation for a VM. Previously, we could change the RAM on the fly:
# xm mem-set 7 256
This was a nice feature, especially for loading new software packages. Since the xm command is gone, the new format is:
# virsh setmem vinci 256000
libvir: QEMU error :
this function is not supported by the hypervisor:
cannot set memory of an active domain

The first thing to notice is the memory must be stated in kilobytes rather than megabytes (how very 80's.) Second, the big nasty error message. In passing, the xm command was issued on an FC6 system, and used the domain number rather than name. In F7 and F8, you would use the name, as in F10.

Will there be a significant impact? Yes. This will impact the density of VMs on a host, but that's assuming the sysad is a perfectionist, like myself. In production, its probably not a big deal. After all, Vmware does not allow dynamic RAM allocation... Until 2009.

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