I have just installed xen server and xen tools, I reboot the system and boot is very slow, when I log in my session it takes a lot of time and HDD led is blinking non-stop. I open a text console and do a free -h and it report having 1.8GB of memmory, when I have 11GB. I have to do a reboot, use the no-xen kernel and I have again 11GB.
I’m reading the docs but I can’t see why is this happenning
For starters, did you install your xen using the YaST virtualization module?
You should do so, to install xen, libvirt, optionally configure a br0 network bridge device (recommend accept) and start with a known good configuration
As with any other hypervisors, every VM gets assigned fixed amount of memory. dom0 is just another (although privileged) VM. Note that dom0 is responsible for processing all IO from all other guests, which means it should not have any workload that is unrelated to that. You do not really do daily work in dom0, you create domU for that.
Actually, only partially true, static memory is allocated by default but the System Administrator doesn’t have to stop there.
Like practically all other virtualization technologies, Xen supports dynamically allocating memory to vms, often automatically “on demand.”
This is the way that I was thinking that it will work.
I have a “normal installation” of opensuse (with KDE, etc)on bare metal, when I installed Xen and boots with the kernel with xen The system boots with my installation in the dom0. What I was thinkig of was using this opensuse in dom0 and installing other machines in domu but you say I should not do that, so I have some questions
Why I should not use dom0 for my opensuse-KDE? It will have effects over the performance of machines in domU? or there are other problems?
If I have to move my opensuse-KDE to domU, I have to make a migration as if migrating from bare metal mchine to VM? or is there other way to do it?
Do not confuse VM virtual memory and host physical memory. These URLs talk about allocating host physical memory to VM. What you see inside VM is virtual memory configured for this VM.
Why I should not use dom0 for my opensuse-KDE? It will have effects over the performance of machines in domU?
Resources consumed by anything running in dom0 won’t be available to handle domU requests. You said the reason to install Xen was performance. It is just logical to minimize possible performance impact on domU by reducing load in dom0.