[CentOS-virt] i386 VM on x86_64 host in Xen

Tue Dec 11 01:20:41 UTC 2007
Christopher G. Stach II <cgs at ldsys.net>

Scott Dowdle wrote:
> Greetings,
> I see these problems with Xen... and many people are stating that they are running CentOS on CentOS... ie Linux on Linux virtualization... so I thought I'd pipe up and mention OpenVZ again.  It does Linux on Linux virtualization well and allows for i386 guests on x86_64 hosts just fine.
> On a dual quad-core Xeon with 16GB of RAM (4GB of swap) I asked the vzsplit command how many machines it thinks my hardware is capable of.  Here's the output:
> [root at comp2 ~]# vzsplit -n 9999999
> On node with 20114 Mb of memory (RAM + swap) 9999999 VEs can not be allocated
> The maximum allowed value is 3795
> On a machine with 2GB of RAM and 4GB of swap:
> [root at backup1 root]# vzsplit -n 9999999
> On node with 6119 Mb of memory (RAM + swap) 999999 VEs can not be allocated
> The maximum allowed value is 639
> Of course, there are some situations where OpenVZ (ie OS Virtualization) isn't suitable... but for the vast majority of common server tasks, it is.  I don't claim you should try that many virtual machines on a single host node but it just goes to show you the density differences possible between Xen and OpenVZ, eh? :)
> TYL,

It would really suck to have 3795 "virtual machines" die all at the same
time from a single kernel panic.

Christopher G. Stach II