[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-users] hvm questions (hvm vs. patched DomU kernel)
Hi folks, i have been doing some tests with xen in the last weeks. First only with patched Kernels in the DomUs, now using the hvmloader, too. I think using the hardware capabilities of the new Intel Dualcore CPUs is not yet very well documented, so i want to ask some questions here. 1. hvmloader vs. vmxloader In the official documentation of xen 3.0 they talk about using the vmxloader to use unmodified DomU kernels. Is this an error in the documentation? http://www.cl.cam.ac.uk/Research/SRG/netos/xen/readmes/user/user.html#SECTION04300000000000000000 I am using hvmloader for my tests as i think that vmxloader belongs to the 2.x version and has been replaced by hvmloader in version 3. 2. Handling of unmodified guests I enjoyed the handling of patched guest os's a much, because the xm console (the virtual serial console) gave me much comfort setting up networking and services in a DomU. Is it possible to use this on unmodified guests too? Do i have to configure a serial port in the virtual machine and do some configuration to create a virtual serial port to connect to with xm console / minicom? Is this documented anywhere? Is it possible to start a virtual machine with a fixed ID? In the config file i give the machine a name, but when i reboot it, it gets a new integer id what means, that the vnc-server for this machine is listening on another port, and as my test box is only reachable via ssh, i must do a new ssh connect with another port forwarding for every time i reboot a virtual machine. 3. Disks (LVM, Files...) I use LVM logical volumes for my DomUs with patched kernels passing them to the domUs as partitions, such as hda1, hda2... The big advantage of this is that i can copy a virtual machine with rsync, then configure the nessecary things using a chroot, leave and power up the machine. Great! Doing backups using LVM snapshots would be something cool, too. Using the hvmloader it seems that this is not possible at all, i can only pass LVM volumes or files as entire disk (hda, hdb) and the guest operating system must partition it. So i am not able to access the files on the virtual disk when the machine is not running, right? Is there any chance to use a similar setup as i use for modified guests? Also i have noticed that i get a disk IO performance of 57Mbyte/sec buffered disk reads with hdparm -tT in a patched domU, nearly the value i get in Dom0, but in a unmodified DomU i get poor results, just about 9Mbyte/sec. What is the reason of this? 4. Recommendation Is it recommendet to use xen with unmodified DomUs when using Linux as virtual machines operating system? I thought it would be faster than patched kernels because the CPU is doing the hard job instead of the kernel patches, but for now it does not seem so. I did not yet do CPU performance tests, so the only thing i have noticed until now is the poor disk io. 5. qemu In my tests i have noticed that when i am using hvmloader the virtualization job is done by a process named "qemu", is this the qemu i know? Was it adapted to work with xen or is it a xen development that has accidently the same name as http://freshmeat.net/projects/qemu/? It would be really great if you could answer my questions. I am wanting to use xen instead of our vmware gsx-server we have now, virtualizing some Windows but mostly Linux servers. In vmware we have io issues with our servers, and the vmware environment produces high load on the host system "without doing anything". Greets Christian Anton _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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