Xen users - Jul 2007 - xen RHEL5/x86_64 @everything installs hang on blocked state

Hi,

I can do a RHEL5/x86_64 anaconda install into a dumU when I select a
few packages only. When I ask for a full install the vm does all the
depedency calculation and then blocks with "Starting install process.
This may take several minutes..."

How can I debug this? How can I find out why the vm blocked? I know
it''s a wait state, but that''s all I know.
-- 
Axel.Thimm at ATrpms.net


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Axel Thimm wrote:
> Hi,
> 
> I can do a RHEL5/x86_64 anaconda install into a dumU when I select a
> few packages only. When I ask for a full install the vm does all the
> depedency calculation and then blocks with "Starting install process.
> This may take several minutes..."
> 
> How can I debug this? How can I find out why the vm blocked? I know
> it''s a wait state, but that''s all I know.
In my former tests we realized a general instability of the
Redhat/Fedora tools to run anaconda inside a DomU. Results where not
always reproducible and often errors occured that could not easily be
debugged.

This seems to be a Fedora-specific issue (we tested a lot of
distributions, and no install tools on no other distribution was that
unreliable) - no wonder Redhat claims Xen to be a not so mature
technology :)

For exactly debugging it, the redhat/fedora Xen list might be a better
place (or, even better, their support teams - this is what you pay for
when using rhel5) to ask.

As a workaround, I can recommend bootstrapping your Rhel5 domU''s with
yum, after mounting the target directory manually - or use something
like xen-tools or FAI - fully automatic installation (both made for
Debian, but both work well on Fedora, and can be nicely combined.

Henning




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On Tue, Jul 10, 2007 at 09:48:47AM +0200, Henning Sprang
wrote:
> Axel Thimm wrote:
> > I can do a RHEL5/x86_64 anaconda install into a dumU when I select a
> > few packages only. When I ask for a full install the vm does all the
> > depedency calculation and then blocks with "Starting install
process.
> > This may take several minutes..."
> > 
> > How can I debug this? How can I find out why the vm blocked? I know
> > it''s a wait state, but that''s all I know.
> 
> In my former tests we realized a general instability of the
> Redhat/Fedora tools to run anaconda inside a DomU. Results where not
> always reproducible and often errors occured that could not easily be
> debugged.
> 
> This seems to be a Fedora-specific issue (we tested a lot of
> distributions, and no install tools on no other distribution was that
> unreliable) - no wonder Redhat claims Xen to be a not so mature
> technology :)
Actually I found the cause and I strongly disagree with the above: The
reason the domU was blocking was because it didn''t have enough memory
in the default setup. Once the memory limits were increased it worked
fine.

But the Old Maid is on xen: No matter what the issue on what
distribution I would expect some way to be able to diagnose and
identify reasons for blocking, at least to some extent.
-- 
Axel.Thimm at ATrpms.net


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Axel Thimm wrote:
> Actually I found the cause and I strongly disagree with the above: 
With which part exactly? (You cited two statements)
> The
> reason the domU was blocking was because it didn''t have enough
memory
> in the default setup. Once the memory limits were increased it worked
> fine.
I think, this is an issue of the Redhat Xen installer(I assume you are
not trying to manually run anaconda somehow but use virt-install), not
Xen in general.

Why?
1) this problem never occured to me with xen-tools on Debian and Yast on
SuSE

2) Sure, a user has always the chance to make wrong settings and break
stuff, but in your case, the writers of the Redhat Xen install scripts
should know how much memory is needed by their anaconda.

So, it is undoubtedly easy to check for them at the very start, and at
least give out a visible warning that you try to run the stuff with not
enough memory, instead of let you run into a strange blocking state.
( In case I missed you writing you found the fix through such a warning,
I admit you that point!)




Henning



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Henning Sprang wrote:
> Axel Thimm wrote:
>
>   
>> Actually I found the cause and I strongly disagree with the above: 
>>     
>
> With which part exactly? (You cited two statements)
>
>   
>> The
>> reason the domU was blocking was because it didn''t have enough
memory
>> in the default setup. Once the memory limits were increased it worked
>> fine.
>>     
>
> I think, this is an issue of the Redhat Xen installer(I assume you are
> not trying to manually run anaconda somehow but use virt-install), not
> Xen in general.
>
> Why?
> 1) this problem never occured to me with xen-tools on Debian and Yast on
> SuSE
>   
Try turning down your RAM for an automated install and selecting a full 
install. It *will* hang, or crash.


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On Tue, Jul 10, 2007 at 11:37:52AM +0200, Henning Sprang
wrote:
> Axel Thimm wrote:
> 
> > Actually I found the cause and I strongly disagree with the above: 
> 
> With which part exactly? (You cited two statements)
Well, if you hadn''t trimmed them I would be able to tell, in doubt
both.
> > The reason the domU was blocking was because it didn''t have
enough
> > memory in the default setup. Once the memory limits were increased
> > it worked fine.
> 
> I think, this is an issue of the Redhat Xen installer(I assume you are
> not trying to manually run anaconda somehow but use virt-install), not
> Xen in general.
> 
> Why?
> 1) this problem never occured to me with xen-tools on Debian and Yast on
> SuSE
> 
> 2) Sure, a user has always the chance to make wrong settings and break
> stuff, but in your case, the writers of the Redhat Xen install scripts
> should know how much memory is needed by their anaconda.
> 
> So, it is undoubtedly easy to check for them at the very start, and at
> least give out a visible warning that you try to run the stuff with not
> enough memory, instead of let you run into a strange blocking state.
> ( In case I missed you writing you found the fix through such a warning,
> I admit you that point!)
I think you sound a bit biased against the Red Hat tools. There is no
special xen treatment in anaconda other than supplying a xen
kernel. And the issue I raised is not solved by blaimg distro A vs
distro X. The issue is

       "How do I find out why xen blocks a guest? What kind of IO
       state is the system waiting on? How can I debug this further?"

For the example at hand this is solved, but what happens when tomorrow
someone comes by and says that the FAI installer is stalled in "b"
state and he has no idea on how to diagnose further xen''s behaviour?
Lecture on how good other distros install?
-- 
Axel.Thimm at ATrpms.net


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