Re: Xen vs. KVM on Debian squeeze
Am 09.12.2012 um 07:48 schrieb P. J. McDermott: I'd like to set up virtualization on a home server with a Debian GNU/Linux squeeze amd64 host and squeeze and wheezy amd64 guests. I'm trying to decide between Xen 4.0 (with paravirtualized guests and probably the xend/xm toolstack) and qemu-kvm 0.12 or 1.1 (with the libvirt tools). 18 months ago I decided against KVM for Xen. Main reason: missing documentation, examples and tools for KVM. The server has two 3.0-GHz CPU cores (an AMD CPU with the AMD-V/SVM virtualization extensions) and 2.0 GiB of RAM (which I'm planning to either double or triple). With Xen 4 you should not go beyond 1 GB memory for each guest. Also we experienced OOM-kills (Out Of Memory) running Dom0 with 256 or 512 MB. Now giving Dom0 1 GB it runs stable. The configuration is a failover cluster using DRBD and pacemaker. 8 VMs with a total allocation of 17 CPUs and 20 GB (hardware is 2 boxes, each has 16 CPUs, 32 GB). We still have a machine like yours (Quadcore @2400 MHz, 4 GB) with Xen 3 in production, running 5 guests with memory allocations between 256 and 1500 MB. I'd like to run at least five guest systems to build software, manage mailing lists, serve files, manage a RAID 5 array using md, etc. That would need a minimum of 6 GB. So I need a virtualization infrastructure that offers efficient CPU and I/O virtualization and allows guest systems to gain or forfeit virtual memory as their loads require (pooling my limited RAM as efficiently as possible). (Ease of understanding and maintenance are nice as well, though I'm happy to read documentation.) Add as much memory as possible (double the estimated amount) - 16 GB. Xen used to have a userspace self-ballooning daemon called xenballoond [4], but it's no longer maintained [5] and it supposedly only supports Red Hat–family systems [6]. Forget all the memory management of running Xen-guests in squeeze/Xen4. All things considered, I'm leaning slightly toward qemu-kvm, because it looks like it'll do what I need in a simple and familiar way; but I'm concerned about the performance of the CPU and I/O virtualization and the page swapping. Squeeze is very outdated now. If you can afford the time, try out both. Helmut Wollmersdorfer -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/bb1f46ac-171f-4e1a-b177-1ba929229...@fixpunkt.de
Re: Xen vs. KVM on Debian squeeze
Hello, I'm using xen on my system too I have an CPU like yours. In the system are 8GB Ram There are three domU everyone with an own ip adress (bridging) I have one domU with 512mb the other ones are with 1024mb ram. the dom0 is running on wheezy. There are no problems at the moment. The domU is running on wheezy too. If your system supports Xen I would use it. But if you know somebody who can help you with kvm if you need than use kvm. Am 13.12.2012 09:49, schrieb Helmut Wollmersdorfer: Am 09.12.2012 um 07:48 schrieb P. J. McDermott: I'd like to set up virtualization on a home server with a Debian GNU/Linux squeeze amd64 host and squeeze and wheezy amd64 guests. I'm trying to decide between Xen 4.0 (with paravirtualized guests and probably the xend/xm toolstack) and qemu-kvm 0.12 or 1.1 (with the libvirt tools). 18 months ago I decided against KVM for Xen. Main reason: missing documentation, examples and tools for KVM. The server has two 3.0-GHz CPU cores (an AMD CPU with the AMD-V/SVM virtualization extensions) and 2.0 GiB of RAM (which I'm planning to either double or triple). With Xen 4 you should not go beyond 1 GB memory for each guest. Also we experienced OOM-kills (Out Of Memory) running Dom0 with 256 or 512 MB. Now giving Dom0 1 GB it runs stable. The configuration is a failover cluster using DRBD and pacemaker. 8 VMs with a total allocation of 17 CPUs and 20 GB (hardware is 2 boxes, each has 16 CPUs, 32 GB). We still have a machine like yours (Quadcore @2400 MHz, 4 GB) with Xen 3 in production, running 5 guests with memory allocations between 256 and 1500 MB. I'd like to run at least five guest systems to build software, manage mailing lists, serve files, manage a RAID 5 array using md, etc. That would need a minimum of 6 GB. So I need a virtualization infrastructure that offers efficient CPU and I/O virtualization and allows guest systems to gain or forfeit virtual memory as their loads require (pooling my limited RAM as efficiently as possible). (Ease of understanding and maintenance are nice as well, though I'm happy to read documentation.) Add as much memory as possible (double the estimated amount) - 16 GB. Xen used to have a userspace self-ballooning daemon called xenballoond [4], but it's no longer maintained [5] and it supposedly only supports Red Hat–family systems [6]. Forget all the memory management of running Xen-guests in squeeze/Xen4. All things considered, I'm leaning slightly toward qemu-kvm, because it looks like it'll do what I need in a simple and familiar way; but I'm concerned about the performance of the CPU and I/O virtualization and the page swapping. Squeeze is very outdated now. If you can afford the time, try out both. Helmut Wollmersdorfer -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/50c9ea0c.2030...@datensumpf.de
Re: Xen vs. KVM on Debian squeeze
P. J. McDermott p...@nac.net wrote: I'd like to set up virtualization on a home server So now you have recommendations both ways :-) Chris -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/jr2mp9x0o8@news.roaima.co.uk
Re: Xen vs. KVM on Debian squeeze
Peter Viskup skupko...@gmail.com wrote: Consider LXC [2] in case you have some concerns of CPU/memory overhead and you plan to run only Linux virtual servers. LXC looks really nice but you need very up-to-date packages, and possibly may even need to consider compiling from source. Issues I've hit so far (none of which is insurmountable): - New kernel to support the memory cgroup option - New libvirt/VMM to support LXC nicely - Templating new hosts is fiddly - Documentation is inconsistent and patchy at best I know I could probably help with at least one of these, so I'm not complaining. However, I don't (yet) have a bleeding-edge installation with which to try out the new components. Cheers, Chris -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/cb3mp9x2s9@news.roaima.co.uk
Re: Xen vs. KVM on Debian squeeze
P. J. McDermott p...@nac.net wrote: I'd like to set up virtualization on a home server with a Debian GNU/Linux squeeze amd64 host and squeeze and wheezy amd64 guests. I'd recommend KVM and libvirt/VMM. The server has two 3.0-GHz CPU cores (an AMD CPU with the AMD-V/SVM virtualization extensions) and 2.0 GiB of RAM (which I'm planning to either double or triple). My home server's running a single twin-core AMD Turion II N40L at 1.5GHz but has 8GB memory. No problems running several servers (at the moment), and has enough clout for me to be seriously considering a virtualised Windows 7 instance, too. So I need a virtualization infrastructure that offers efficient CPU and I/O virtualization and allows guest systems to gain or forfeit virtual memory as their loads require (pooling my limited RAM as efficiently as possible). I have relatively small memory allocations to the guests (~2GB) but with the balloon driver installed in case I need to tweak on the fly. I figure that a less-used guest will get pushed out to the host's swap if things start getting squeaky. I'm not sure I like the idea of freeing memory by swapping, but at least it's a simple design and easy to set up. Is there a newer method in KVM (in Debian squeeze or squeeze-backports) of automatically growing and shrinking guest systems' virtual memory space in RAM, preferably without using swap? I had originally understood that this is what the balloon driver allowed, but I haven't found a way of controlling it automatically based on the host's available memory. Ah, http://aglitke.wordpress.com/2011/03/03/automatic-memory-ballooning-with-mom/ might be worth following through. All things considered, I'm leaning slightly toward qemu-kvm, because it looks like it'll do what I need in a simple and familiar way; but I'm concerned about the performance of the CPU and I/O virtualization and the page swapping. What I like about KVM/libvirt is that it (now) handles LVM as a volume pool, so I don't need to use large files in the filesystem to hold guests' backing store. What I don't like about KVM is its dependence on the backing store being an entire virtual disk, complete with partition table, etc. It makes growing filesystems an absolute pain (LVM resize, guest shutdown, fdisk/parted on partition file, resize guest filesystem, restart guest), but I don't do it too often. I also keep the filesystem layouts for my guests' primary disk as simple as possible (typically the everything in one big filesystem approach). What I do like about KVM is its ability to run non-aware guests. I have lost track of whether Xen would let me run an instance of Windows 7, for example. If you do go for KVM/libvirt, I would recommend the virtualised disk and network devices. Empirically they work well, and gut feel (i.e. not quantitatively) suggests that at worst they won't be any slower than emulations of physical devices and actually might be a little faster and/or more efficient. Chris -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/loejp9xs4r@news.roaima.co.uk
Re: Xen vs. KVM on Debian squeeze
Greetings, On Tue, Dec 11, 2012 at 10:33 AM, Chris Davies chris-use...@roaima.co.uk wrote: P. J. McDermott p...@nac.net wrote: I'd like to set up virtualization on a home server with a Debian GNU/Linux squeeze amd64 host and squeeze and wheezy amd64 guests. I'd recommend KVM and libvirt/VMM. I'd go for Xen. Not a virtualization expert, but i've installed a simple dom0 on squeeze with a sid PVM, on async raid1 with LVM; all through the debian instaler, no trouble. YMMV What I like about KVM/libvirt is that it (now) handles LVM as a volume pool, so I don't need to use large files in the filesystem to hold guests' backing store. You can use LVM with Xen too. What I do like about KVM is its ability to run non-aware guests. I have lost track of whether Xen would let me run an instance of Windows 7, for example. Xen supports HVMs, if the host CPU supports virtualization. You can also use pv-drivers to speed things up. Just my 2c. HTH, Nuno -- On the internet, nobody knows you're a dog. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/CADqA9uYgy7DVA0C52Coa9HeRKj=0hva3fjljirt9bje6sto...@mail.gmail.com
Re: Xen vs. KVM on Debian squeeze
On 12/09/2012 07:48 AM, P. J. McDermott wrote: Hi, I'd like to set up virtualization on a home server with a Debian GNU/Linux squeeze amd64 host and squeeze and wheezy amd64 guests. I'm trying to decide between Xen 4.0 (with paravirtualized guests and probably the xend/xm toolstack) and qemu-kvm 0.12 or 1.1 (with the libvirt tools). My experience in this area is currently limited; I've only used qemu-kvm 0.12, and only through Virtual Machine Manager. So I'm looking for some advice and answers to help me decide how to set this up. The server has two 3.0-GHz CPU cores (an AMD CPU with the AMD-V/SVM virtualization extensions) and 2.0 GiB of RAM (which I'm planning to either double or triple). I'd like to run at least five guest systems to build software, manage mailing lists, serve files, manage a RAID 5 array using md, etc. So I need a virtualization infrastructure that offers efficient CPU and I/O virtualization and allows guest systems to gain or forfeit virtual memory as their loads require (pooling my limited RAM as efficiently as possible). (Ease of understanding and maintenance are nice as well, though I'm happy to read documentation.) I see that KVM supports a rather simple method of overcommitting memory [1], relying on Linux's lazy page allocation and swapping [2][3]. [1]: http://www.linux-kvm.org/page/FAQ#Is_dynamic_memory_management_for_guests_supported.3F [2]: http://www.linux-kvm.org/page/Memory [3]: https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Administration_Guide/sect-Virtualization-Tips_and_tricks-Overcommitting_with_KVM.html I'm not sure I like the idea of freeing memory by swapping, but at least it's a simple design and easy to set up. Is there a newer method in KVM (in Debian squeeze or squeeze-backports) of automatically growing and shrinking guest systems' virtual memory space in RAM, preferably without using swap? Xen used to have a userspace self-ballooning daemon called xenballoond [4], but it's no longer maintained [5] and it supposedly only supports Red Hat–family systems [6]. [4]: http://blog.xen.org/index.php/2008/08/27/xen-33-feature-memory-overcommit/ [5]: http://old-list-archives.xen.org/archives/html/xen-devel/2011-02/msg01333.html [6]: http://xenbits.xen.org/hg/xen-unstable.hg/file/91232efdcfdc/tools/xenballoon/xenballoond.README Now Xen supports Transcendent Memory or tmem (self-ballooning and frontswap self-shrinking) [7][8] instead. [7]: https://lwn.net/Articles/454795/ [8]: drivers/xen/xen-selfballoon.c in Linux 3.1 or later The tmem code is in the version of Linux in squeeze-backports, and the XEN_BALLOON option is enabled. But, as far as I can tell, CLEANCACHE, XEN_SELFBALLOONING, and FRONTSWAP are disabled. I'd rather not have to rebuild the Linux packages to install in my squeeze and wheezy domUs for this. All things considered, I'm leaning slightly toward qemu-kvm, because it looks like it'll do what I need in a simple and familiar way; but I'm concerned about the performance of the CPU and I/O virtualization and the page swapping. Can anyone show me that I've overlooked something about Xen in Debian or convince me that qemu-kvm will perform fine for my needs? Thanks, I would recommend you to go with Wheezy at least for dom0. It provides the XCP toolstack which is the new standard of Xen management in Debian. This will save you a lot of time as it is totally different from xend/xm toolstack. It doesn't make sense for you to learn xend/xm from scratch just for three-four upcoming months. The other thing with Squeeze version of linux-kernel there was strange bug discovered [1] causing the dynamic memory increase not working properly. It is not experienced on Wheezy. Consider LXC [2] in case you have some concerns of CPU/memory overhead and you plan to run only Linux virtual servers. [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=693851 [2] http://wiki.debian.org/LXC -- Peter Viskup -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/50c7900a.80...@gmail.com
Xen vs. KVM on Debian squeeze
Hi, I'd like to set up virtualization on a home server with a Debian GNU/Linux squeeze amd64 host and squeeze and wheezy amd64 guests. I'm trying to decide between Xen 4.0 (with paravirtualized guests and probably the xend/xm toolstack) and qemu-kvm 0.12 or 1.1 (with the libvirt tools). My experience in this area is currently limited; I've only used qemu-kvm 0.12, and only through Virtual Machine Manager. So I'm looking for some advice and answers to help me decide how to set this up. The server has two 3.0-GHz CPU cores (an AMD CPU with the AMD-V/SVM virtualization extensions) and 2.0 GiB of RAM (which I'm planning to either double or triple). I'd like to run at least five guest systems to build software, manage mailing lists, serve files, manage a RAID 5 array using md, etc. So I need a virtualization infrastructure that offers efficient CPU and I/O virtualization and allows guest systems to gain or forfeit virtual memory as their loads require (pooling my limited RAM as efficiently as possible). (Ease of understanding and maintenance are nice as well, though I'm happy to read documentation.) I see that KVM supports a rather simple method of overcommitting memory [1], relying on Linux's lazy page allocation and swapping [2][3]. [1]: http://www.linux-kvm.org/page/FAQ#Is_dynamic_memory_management_for_guests_supported.3F [2]: http://www.linux-kvm.org/page/Memory [3]: https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Administration_Guide/sect-Virtualization-Tips_and_tricks-Overcommitting_with_KVM.html I'm not sure I like the idea of freeing memory by swapping, but at least it's a simple design and easy to set up. Is there a newer method in KVM (in Debian squeeze or squeeze-backports) of automatically growing and shrinking guest systems' virtual memory space in RAM, preferably without using swap? Xen used to have a userspace self-ballooning daemon called xenballoond [4], but it's no longer maintained [5] and it supposedly only supports Red Hat–family systems [6]. [4]: http://blog.xen.org/index.php/2008/08/27/xen-33-feature-memory-overcommit/ [5]: http://old-list-archives.xen.org/archives/html/xen-devel/2011-02/msg01333.html [6]: http://xenbits.xen.org/hg/xen-unstable.hg/file/91232efdcfdc/tools/xenballoon/xenballoond.README Now Xen supports Transcendent Memory or tmem (self-ballooning and frontswap self-shrinking) [7][8] instead. [7]: https://lwn.net/Articles/454795/ [8]: drivers/xen/xen-selfballoon.c in Linux 3.1 or later The tmem code is in the version of Linux in squeeze-backports, and the XEN_BALLOON option is enabled. But, as far as I can tell, CLEANCACHE, XEN_SELFBALLOONING, and FRONTSWAP are disabled. I'd rather not have to rebuild the Linux packages to install in my squeeze and wheezy domUs for this. All things considered, I'm leaning slightly toward qemu-kvm, because it looks like it'll do what I need in a simple and familiar way; but I'm concerned about the performance of the CPU and I/O virtualization and the page swapping. Can anyone show me that I've overlooked something about Xen in Debian or convince me that qemu-kvm will perform fine for my needs? Thanks, -- P. J. McDermott http://www.pehjota.net/ http://www.pehjota.net/contact.html -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/50c43459.9080...@nac.net
