On Sun, Jun 01, 2008 at 06:08:31PM +0100, Ewan MacMahon wrote:
> > -----Original Message-----
> > From: Testbed Support for GridPP member institutes
> >
> > In Jan 2008 there was this in rollout about problems with WN
> > on Xen VM:
> >
> >
> > > Xen is not able to cope with tls libraries. So I suggest you to not
> > > install UI/WN inside a xen virtual machine.
> >
> > As Xen & LCG mware are both moving targets, that may be fixed
> > (or not) by now.
> >
> I've just had a look back at that thread and as far as I can see it's a
> total non-issue; Xen paravirtualised guests can never run with the TLS
> version of glibc in them[1]; it's not a bug, it's not a gLite specific
> matter,
> and it's well doucumented, e.g. in the Xen FAQ, which also points out
> that
> if you do this, Xen gives you "A large warning message":
> http://wiki.xensource.com/xenwiki/XenFaq#head-31ebe1eb6c34c5d4044559364d
> 1048bf8ea1cae7
>
> So; in short, it seems that the person having the problem set up their
> guest in a way that would be broken regardless of what they used it for,
> used it for gLite, and got a broken gLite. I wouldn't worry about it,
> just don't do the same thing.
Disabling TLS *will* cause problems, the bdb depends on it for example
for locking and openldap will fail if you do that. The RedHat versions
that support xen install /etc/ld.so.conf.d/kernel*.conf which tell the
linker how to do the right thing for xen. As Ewan says you don't have
to do anything.
> > On next stage of Bristol HPC we may need to try WN in VM - probably
> > not Xen - since the HPC WN won't run SL4; possibly run SL5 or some
> > other OS.
> >
> I'd have thought Xen would be the obvious candidate; it's a standard
> issue
> part of SL/CentOS/RHEL 5, which has got to be an easier sell than
> getting
> something else installed?
XenU PV support was added in 4.6 and it's working fine under 5.x so you
shouldn't worry about problems there.
In addition the 4.7 beta introduced support for the PV drivers under
HVM and tick divider capability[2] so you can run fully virtualized
with minimal performance loss over the para virtualized case.
Cheers,
Kostas
> [1] The separate TLS glibc is gone in more recent Linux systems, those
> seem to run
> on top of Xen without modification.
[2]
http://kbase.redhat.com/faq/FAQ_103_12581.shtm
http://www.arrfab.net/blog/?p=62
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