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

2007-12-11 Thread Scott Dowdle 
Christopher,

- Christopher G. Stach II [EMAIL PROTECTED] wrote:
 It would really suck to have 3795 virtual machines die all at the
 same time from a single kernel panic.

Yes, absolutely it would.  I use the OpenVZ kernels that are based on the RHEL4 
and RHEL5 kernels and I haven't had any problems with them... just like I 
haven't had any problems with the stock RHEL4 and RHEL5 kernels... nor CentOS 
kernels.

I usually end up rebooting host node machines because of kernel upgrades... so 
my machines don't get a chance to have longish uptimes... but on one remote 
colocation machine I have for hobby stuff... it currently has an uptime of 106 
days.  It has 7 VPSes on it and they are fairly fat as they all run a full set 
of services.  I know I've been running that machine for close to 2 years now... 
and if I remember correctly it started out with CentOS 4.0.  I've upgraded to 
each release (on the host node and the VPSes) and am currently at CentOS 4.5.  
I look foward forward to 4.6.

Here's what they look like (ip addresses and hostnames obscured):

[EMAIL PROTECTED] ~]# vzlist
  VEID  NPROC   STATUS IP_ADDR HOSTNAME
   101 53runningxx.xx.xx.xxvps101.localdomain
   102 44runningxx.xx.xx.xxvps102.localdomain
   103 44runningxx.xx.xx.xxvps103.localdomain
   104 32runningxx.xx.xx.xxvps104.localdomain
   105322   runningxx.xx.xx.xxvps105.localdomain
   106 32runningxx.xx.xx.xxvps106.localdomain
   107 29runningxx.xx.xx.xxvps107.localdomain

Looking at the number of processes, can you tell which VPS is running Zimbra? :)

6 of the 7 VPSes are CentOS and the remaining 1 is Debian.

Speaking of uptimes, I have a legacy machine at work running Linux-VServer on 
a 2.4.x series kernel.  It had the longest uptime of any machine I've had... 
and was well over 400 days... when a power outage that outlasted its UPS took 
it down.  That particular machine runs three VPSes that are mail 
relay/frontends and they get pounded... so that uptime is notable.

So, my experience has been that physical failures and power failures (although 
pretty rare) are more common that kernel panics that take down all of my 
virtual machines.

TYL,
-- 
Scott Dowdle
704 Church Street
Belgrade, MT 59714
(406)388-0827 [home]
(406)994-3931 [work]
___
CentOS-virt mailing list
CentOS-virt@centos.org
http://lists.centos.org/mailman/listinfo/centos-virt

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

2007-12-11 Thread Daniel de Kok 
On Tue, 2007-12-11 at 11:27 -0500, Scott Dowdle wrote:
 There are uses where Xen is much better suited and OpenVZ isn't even a
 viable option.  But there are other cases where OpenVZ is a better fit
 especially with regards to density and scalability.  OpenVZ is also
 very attractive in those situations where you want to isolate a single
 or a small number of services... although the vast majority if my
 deployments have a full set of services.

Yes. It's good not to underestimate OS-level virtualization. Many people
used chroot to isolate certain processes. OS-level virtualization
provides better isolation and control, at only little extra cost.

Operating systems that provide binary compatibility for other systems
(like the BSDs or Solaris) can also use OS-level virtualization to
emulate a complete enviroment that resembles the emulated system.

The downside of most (if not virtually all) current OS-level
virtualization on Linux is that they do not have proper support for
SELinux. I suppose that things get more interesting in that respect when
container features are integrated in the mainline kernel.

-- Daniel

___
CentOS-virt mailing list
CentOS-virt@centos.org
http://lists.centos.org/mailman/listinfo/centos-virt