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New to the list ... Looking for any recommendations inre: VMWare Vs. Xen
by Holtz,Robert 09 Nov '07

09 Nov '07

I'm new to the CentOS arena and I'm curious as to what virtualization products are preferred? The two main ones that I know of are Xen and VMWare. VMWare seems to be the most capable inre: number and size of vm's allowed. When looking at Xen it appears that since Citrix acquired them the free version is cripple-ware and is very restrictive. Thanks in advance for any information. If you are not the intended recipient of this message (including attachments), or if you have received this message in error, immediately notify us and delete it and any attachments. If you no longer wish to receive e-mail from Edward Jones, please send this request to messages(a)edwardjones.com. You must include the e-mail address that you wish not to receive e-mail communications. For important additional information related to this e-mail, visit www.edwardjones.com/US_email_disclosure

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Initrd for Domu
by Franco Spinelli 28 Oct '07

28 Oct '07

I am using a DomU CentOS 5 installed on a LVM file. I have kernel files in Centos DomU (/boot) and I am using pygrub for booting. Using default initrd file DomU don't boot Making a new initrd file using --preload xebblk --preload --xennet DomU boot ok. Is this correct? If is correct, how can I automate initrd production when I get a kernel update? Regards Franco Spinelli

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networking problems with kernel 2.6.18-8.1.15.el5xen
by Johnn Tan 25 Oct '07

25 Oct '07

Today I installed a core CentOS-5 (--nobase). After that, I "yum update", rebooted, then "yum install xen kernel-xen". When I boot into the xen kernel, I can't get networking on eth0. It can ping itself, but not anything else. There are no routes listed, when I try to add a default gateway, it just says there's no network reachable. When I change /boot/grub/grub.conf back to non-xen kernel (same version), networking works again. Has anyone else updated to the latest CentOS-5 xen kernel? johnn

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Xen/VMWare Server comparison and "best Xen practices"?
by Kai Schaetzl 19 Oct '07

19 Oct '07

I'm wondering what others who have already used the Xen kernel for DomUs and the (free) VMWare Server can say about the comparison in actual day-to-day operation. I've only started playing with Xen on CentOS 5 and I've been running VMWare Server only on Win2k3 servers so far, so I'm missing direct comparibility. I find that VMWare is highly reliable and flexible, but needs a good portion of RAM and CPU for working nicely. Xen seems to be less reliable, but more responsive on low ressources. It's also more flexible when you want to move it around as it is all stored in a single file and the config file takes only a few options. Xen is supposed to give "almost the same performance" as if not virtualized. I get confusing figures from the Virtual Machine Manager. On my test machine the Dom0 takes about 9% of the CPU with one VM when both are mostly idle. Top says that 3% of that is taken by the X-Server, most of the rest is shared by two python processes (which belong to Xen I suppose) and xenstored. (The test machine is on a single Athlon 2500+ or around that, not sure about the exact speed.) But regularly one of the python processes grabs another 10-15%, so the whole CPU utilization goes up to around 20%. Although the single VM is idle at that time and shows 0.0x%. So, even when idle the whole CPU utilization zigzags between 10 and 20%. I found that when I close the VM console that drops to 2-3%, so that python process is obviously related to the VM console. The interesting thing is that when I then reopen the console from the VM manager it keeps going at about 3% and doesn't go up to the earlier 9%. But it still zigzags between 3 and 11% then. All the figures have been taken from the VM manager. The %us count in top seems to stay at 3% all the time. With less reliable I refer to a filesystem problem that seems to occur sometimes after rebooting/shutdown. Sometimes after rebooting there either is no filesystem file anymore (which is not healable, of course) or the kernel panics with a filesystem problem on first boot or reboot, but may boot just fine after a second or third try. The problem that the filesystem file is just gone seems to happen only when I reboot/shutdown from within the console with the shutdown/reboot command. For instance it can happen if I let it do the first reboot after I installed the OS on the VM. When I "xm shutdown" or CRTL+ALT+DEL or hit the shutdown button on the Virtual Machine Manager it does not *seem* to happen (maybe I just didn't shutdown often enough to see it happen there as well.) I've already lost several testing VMs because of this. I wonder if this problem might happen because I use the option of not allocating all space in the filesystem file right-away. I also wonder if performance might be better if it wouldn't need to grow. So, are there recommended best practices for Xen VMs like "always use partitions", "always allocated whole space at once", "never shutdown from the console window", "never use virtual machine manager" or some such? Kai -- Kai Schätzl, Berlin, Germany

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OS Virtualization: Linux-VServer and OpenVZ
by Scott Dowdle 12 Oct '07

12 Oct '07

Greetings, So, anyone on this list using OS Virtualization? I've been using OpenVZ for about 1.5 years. I also have some experience with Linux-VServer. In my experience, if you want to do Linux on Linux, both OpenVZ and Linux-VServer offer native performance, better scalability, and higher density than VMware, Xen or KVM... although I must admit I haven't actually tried KVM yet. If anyone has any questions about OpenVZ and/or Linux-VServer, feel free to ask. I have a couple of screencasts I've done, and interview with the OpenVZ project manager, and coming soon, an interview with the Linux-VServer project leader. TYL, -- Scott Dowdle 704 Church Street Belgrade, MT 59714 (406)388-0827 [home] (406)994-3931 [work]

2 1

Xen crash
by Nicolas Sahlqvist 09 Oct '07

09 Oct '07

Hi Centos-virt, I'm new to this list and joined since I am volunteering as a tech admin for a non profit organization called CouchSurfing (.com) where we tried to move the web servers to Xen zones and this has proven quite unstable since the our defined zones tends to crash on a daily basis with the latest CentOS 5 Xen updates. The physical boxes have 2 quad core 1.6GHz Xeon CPU's and 4 GB RAM, there is currently only 1 domain on each box, configured with 2.2GB RAM. Domain 0: [root@nd10254 ~]# rpm -qa | grep xen xen-libs-3.0.3-25.0.4.el5 kernel-xen-2.6.18-8.1.8.el5 kernel-xen-2.6.18-8.1.14.el5 xen-3.0.3-25.0.4.el5 Web1: [root@web1 ~]# rpm -qa | grep xen kernel-xen-2.6.18-8.1.8.el5 kernel-xen-2.6.18-8.1.14.el5 The Domain0 zone is indeed rock stable, while the Web1 etc. are crashing daily with the 2.6.18-8.1.14 Xen kernel and the stack trace we see after a few hours is as follows: BUG: soft lockup detected on CPU#5! Call Trace: <IRQ> [<ffffffff802a76ad>] softlockup_tick+0xdb/0xed [<ffffffff8026ba66>] timer_interrupt+0x396/0x3f2 [<ffffffff80210a87>] handle_IRQ_event+0x2d/0x60 [<ffffffff802a79ec>] __do_IRQ+0xa4/0x105 [<ffffffff802699b3>] do_IRQ+0xe7/0xf5 [<ffffffff8038dde8>] evtchn_do_upcall+0x86/0xe0 [<ffffffff8025cc1a>] do_hypervisor_callback+0x1e/0x2c <EOI> [<ffffffff802063aa>] hypercall_page+0x3aa/0x1000 [<ffffffff802063aa>] hypercall_page+0x3aa/0x1000 [<ffffffff8026afe2>] raw_safe_halt+0x84/0xa8 [<ffffffff802684f8>] xen_idle+0x38/0x4a [<ffffffff80247bcd>] cpu_idle+0x97/0xba BUG: soft lockup detected on CPU#7! Etc., etc etc, It does not crash the Xen zones directly, but clogs up the Xen web1 console etc. We did not see this when running the 2.6.18-8.1.8 Xen kernel, instead the Xen zones crashed less frequent with a out of memory problem as follows: Call Trace: [<ffffffff802aeefc>] out_of_memory+0x4e/0x1d3 [<ffffffff8020efe8>] __alloc_pages+0x229/0x2b2 [<ffffffff8023fd5b>] __lock_page+0x5e/0x64 [<ffffffff80232637>] read_swap_cache_async+0x42/0xd1 [<ffffffff802b32a2>] swapin_readahead+0x4e/0x77 [<ffffffff8020929d>] __handle_mm_fault+0xae3/0xf46 [<ffffffff80260709>] _spin_lock_irqsave+0x9/0x14 [<ffffffff80262fe8>] do_page_fault+0xe48/0x11dc [<ffffffff80207138>] kmem_cache_free+0x77/0xca [<ffffffff8025cb6f>] error_exit+0x0/0x6e We think the whole problem is how the kernel fails to handle resource cloging (to many interrupts, heavy CPU and memory usage in the defined zones etc.) from stubmbling on some fuzzy posts on the net, example: http://article.gmane.org/gmane.comp.emulators.xen.user/26617 Is this problem known to you or new, any ideas on howto resolve it? Regards, Nicolas Sahlqvist CouchSurfing,.com

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Re: [kvm-devel] [RFC] let kvm be compiled with gcc4 and prevent users to shoot themselves in the foot while doing so (was Re: [ kvm-Bugs-1807620 ] KVM's --disable-gcc-check doesn't work)
by Jim Paris 08 Oct '07

08 Oct '07

Carlo Marcelo Arenas Belon wrote: > And considering also there might be other yet unknown bugs because of gcc4, it > is most likely better to stick to use gcc-3.x, unless there is really no other > option. > > For cases where no compat-gcc package is provided (like in OpenSUSE) then the > following is IMHO the next best approach to force users to get gcc-3.x > compiler installed from source just to be able to compile kvm. This will probably become more of a problem over time. GCC 3 is slated to be removed from the next Debian release: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=440425 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=440430 > PS. please let me know what you think about it and if interested so I can > provide the 3 patches (or more if more changes are needed) in a [PATCH] > series for easy git-am'ing > > + if test $check_gcc = "no" ; then > + if gcc -v 2>&1 | grep -q 'gcc *version *4\.[0-3]\.[0-9]'; then > + echo "#define USE_GCC4 1" >> $config_h > + fi > + fi Something like #if __GNUC__ >= 4 in the code would be simpler. -jim

1 0

Windows 98 with Xen?
by Ken Tang 06 Oct '07

06 Oct '07

Anyone successful at installing Windows 98 on Xen in CentOS5? I get an error about Windows 98 not being able to find a compatible CD drive. I use an .ISO image as the CD.

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Re: [kvm-devel] [ kvm-Bugs-1807620 ] KVM's --disable-gcc-check doesn't work
by Farkas Levente 05 Oct '07

05 Oct '07

Gregory Haskins wrote: > On Thu, 2007-10-04 at 19:27 +0200, Farkas Levente wrote: > >> ok but now as qemu code was imported into kvm, then it's probably would >> be better to witch gcc-4.x? > > Sure. Are you volunteering? ;) I'm sure both upstream QEMU developers, > KVM developers, and the community using either would be most > appreciative. I know I would be. here i mean that packaging kvm for fedora/redhat/centos using gcc-4.x in stead of gcc-3.x. if currently there is no reason to use gcc-3.x than i change all of my spec file. ps. anyway it's planed to be temporary or permanent to use a qemu fork for kvm and not try to propagate changes back to the upstream qemu? -- Levente "Si vis pacem para bellum!"

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VMGL for centos and fedora
by Farkas Levente 29 Sep '07

29 Sep '07

hi, is there any plan to package and/or include VMGL in centos/fedora: http://www.cs.toronto.edu/~andreslc/xen-gl/ -- Levente "Si vis pacem para bellum!"

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