[COLUG] VMware vs Xen Enterprise

[Duane]

Brian Miller wrote:

> I haven't use Enterprise XEN, but I have worked a bit with the standard
> XEN that ships with Linux.  You'll loose a lot of flexibility if you go
> with XEN.  The management interface is much harder to work with, and it

Technically there isn't a management interface that comes with Xen,
there are some third party ones you can buy as well as some open source
ones, they all have their pros and cons, on the other hand I believe the
enterprise version however does come with a management interface similar
to the VMWare stuff.

> prevents you from doing some reasonable things.  On an initial install
> with XEN, the guest boots from the CDROM without a problem.  I have yet
> to figure out how to get the guest to boot from CDROM once the OS is
> installed (say, to run a rescue disk on it).  On VMWare this is a piece
> of cake.

Why would you want or need to try and boot from a CDROM?

Why don't you just mount the partition and chroot if you need to, I
really like the way Xen works because it's really really really
difficult for most users to break the boot up even if they have root access.

> If your host system doesn't have lots of memory, VMWare also allows you
> to over-subscribe RAM (you can create 10 guests with 1GB each in a
> system with 8GB of RAM).  And just because you give a guest 1GB does not
> mean it will use all of it (especially if all of your guests are running
> the same OS).  With XEN, once you allocate RAM to a guest, it is no
> longer available to the host.

If you want to over utilise ram, use OpenVZ instead. The downside to
this is you can't cache disk to ram which is a big plus in my book
because one of the bigger issues with virtualisation is disk IO causing
the system to block, the more ram the more you can cache the less you
need to re-read from disk all the time.

Someone likened this to hitting a cement barrier on a highway that you
can't see, since you never exactly know where or when you are going to
hit the ram limit and you can suddenly slam into it and the processes
start getting killed off by the system.

-- 

Best regards,
 Duane

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