vizz.info

Just noticed an interesting quirk with VMWare Server and hyper threading CPUs

I told my VM to use 1 CPU but CentOS 4 install detected the underlying hardware CPU had hyper threading so installed the SMP kernel !

Linux localhost.localdomain 2.6.9-67.0.15.ELsmp #1 SMP Thu May 8 10:52:19 EDT 2008 i686 i686 i386 GNU/Linux

as opposed to creating a VM where underlying hardware didn’t have hyper threading where CentOS 4 install just installed the basic kernel !

Linux localhost.localdomain 2.6.9-67.0.15.EL #1 Thu May 8 10:39:19 EDT 2008 i686 i686 i386 GNU/Linux

Apparently there is a problem in the kernel used in Red Hat RHEL 4&5, CentOS 4&5, OEL 4&5, SUSE, Ubuntu 7 and other GNU/Linux distributions that causes EXT2 EXT3 filesystems that are residing on SANs to randomly go read-only !

However if you are using kernel 2.6.18-53.1.21+ or  2.6.22+ you should be ok !

See Red Hat

• https://rhn.redhat.com/errata/RHSA-2007-0014.html
• http://kbase.redhat.com/faq/FAQ_85_10846.shtm
• http://kbase.redhat.com/faq/FAQ_85_9610.shtm
• https://bugzilla.redhat.com/show_bug.cgi?id=213921

See VMware

• http://communities.vmware.com/message/752884
• http://kb.vmware.com/selfservice?externalId=1001778
• http://kb.vmware.com/selfservice?externalId=51306

If you are using CentOS 5 , Oracle Enterprise 5 or Red Hat Enterprise 5 as a VMware host or guest you can edit /etc/yum.conf and add a line

exclude=kernel*

this should prevent yum updating your kernel and thus breaking vmware services modules in vmware server and vmware services modules in vmware guest tools

also see

http://www.linuxmanpages.com/man5/yum.conf.5.php

http://linux.die.net/man/5/yum.conf

There is an OpenVZ live-CD VZ VM server with VZ VM guests (based on CentOS or KNOPPIX) that you can download from http://wiki.openvz.org/Download_live_CD

And there is a quick start guide to read at http://wiki.openvz.org/Getting_started_with_OpenVZ_live_CD

Xen

http://fedoraproject.org/wiki/Tools/Xen

CentOS4, FC6, RHEL 4

http://fedoraproject.org/wiki/FedoraXenQuickstartFC6

CentOS5, FC7, RHEL 5

http://fedoraproject.org/wiki/Docs/Fedora7VirtQuickStart

http://www.virtualization.info/ continues to be a source of some of the best virtualisation articles available
http://www.virtualization.info/2007/01/hidden-risk-of-virtual-appliances.html

http://www.virtualization.info/2006/12/choosing-between-vmware-server-and-esx.html
http://www.virtualization.info/2007/11/thinsy-announces-7th-xen-based.html

http://www.virtualization.info/2007/11/red-hat-adopts-xen-31-in-its-new.html

http://www.virtualization.info/2007/11/whitepaper-understanding-full.html

( http://www.vmware.com/files/pdf/VMware_paravirtualization.pdf )