[Fedora-xen] Formatting pauses during install

[Tarun Reddy]

On Jun 12, 2007, at 8:08 PM, Tarun Reddy wrote:

>
> On Jun 12, 2007, at 4:56 PM, Tom Horsley wrote:
>
>> On Tue, 12 Jun 2007 12:16:44 -0600
>> Tarun Reddy <treddy at rallydev.com> wrote:
>>
>>> I'm using Centos 5 dom0 on an x86_64 machine with 12GB of RAM.
>>>
>>> Tried to use virt-manager to install a Centos 4 domU (also tried  
>>> with
>>> Centos 5 domU) but the tool limits the disk to 16000 MB. So  
>>> switch to
>>> using virt-install and specified an 80GB disk. Everything proceed
>>> well until "Formatting / file system" which stops at 11% (~8GB of  
>>> the
>>> 74GB / partition).
>>
>> Seems likely it might be the same bug as:
>>
>> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=234160
>>
>> If you look at the VM you are trying to install in the virt-manager
>> app, is it using as much CPU as it can get?
>>
> Thank you for the pointer! The load on the host shows 1 x number of  
> guest hosts during those pauses. It did eventually finish the  
> install but it took almost 2 hours with a local Centos mirror!
>
> So looking at the bugzilla report, I noticed I didn't mention that  
> I was using paravirtualized guest domains. Of course, the bug in  
> bugzilla originally references fully virtualized guests. So, on a  
> whim, I try a Centos 4.5 guest os fully virtualized. Apart from  
> having to add noapic to my kernel boot line, it seems much more  
> stable with no pauses at all. Go figure.
>
> I was hoping to use a paravirtualized since I thought it might be  
> faster.
>
> Of course on a 32 bit Intel box (older Xeons), I have no issues  
> with paravirtualized hosts, either Centos 5 or 4.5.
>

Less baffled now.

The difference between the pause state and non-paused state is *not*  
para versus fully virtualized systems as I thought. Rather it was  
sparse versus non-sparse disk images.

I had started using virt-install since I couldn't get virt-manager to  
set up a disk image bigger that 16GB. By default virt-install uses  
sparse disks (versus virt-manager which defaults to non-sparse  
disks). Hence, the dramatic pauses that involved anything large I/O  
to the disk. Fortunately, there are nice command line switches that  
allow changing of that and I am now running paravirtualized Centos 5  
guest without pauses (Centos 4.5 installing as we speak).

Thanks for your help!
Tarun