Re: xen & kernel pae

I think 32-bit Xen is limited to only 16G of physical RAM.  This still leaves 
1G to account for; a possible guess would be that you have a *very* large 
memory hole on your system and that's pushing the addresses of the real 
physical RAM up to where Xen can't use them 

64-bit Xen should be able to access all your memory, I think.  And you should 
be able to run 32-bit PAE guests in any part of that memory; they may even be 
able to grow beyond 16G but I'm not sure on that point.

Cheers,
mark

On Monday 28 April 2008, Marco Strullato wrote:
> Hi all, I'm installing xen 3.0 (supplied with centos 5.0) into a
> xerver with 26GB of ram.
> I know that xen kernel has "pae" built in but the problem is that the
> hypervisor can "see" only 15GB.
> I tried also to pass a parameter at boot: mem=26G. Nonthing has
> changes, the system can manage only 15GB of RAM.
>
> Do you know why?
>
> Thanks
>
> Marco
>
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Re: can't create domU in Ubuntu - Floating point error

> I just installed Ubuntu 8.04-server-amd64 and want to get a CentOS domU
> installed, but virt-install keeps on failing with Floating Point exception:
>
> root <at> venus:~# virt-install -v --name=vps02 --file=/home/vps02.img
> --file-size=10 --ram=512
> Floating point exception

Well, that's weird!  I think I'd suggest filing a bug against the Ubuntu 
package.  It's not something I've heard of happening before, so it's possible 
that it's specific to your situation, or to the particular version of the 
tool you're using.

Daniel: hope you don't mind me cc-ing, I wondered if you might have a hint for 
us?

Cheers,
Mark

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Re: Re: virt-manager on windows

> have you considered the possibility of running over SSH to an Xming server
> on the windows box?
>
> have a look at:
>
> http://www.freesoftwaremagazine.com/articles/run_any_gnu_linux_app_on_windo
>ws_without_any_virtualization http://www.straightrunning.com/XmingNotes/

I think this would work well.  Xming is very simple to use and would integrate 
well with your existing Windows desktop.  It'd be good for admin stuff other 
than virt-manager too 

Cheers,
Mark

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Re: Migration and checkpointing

The -c option to xm save doesn't handle the checkpointing of storage *at all*.  
As such, you're free to use any form of storage checkpointing you want.  The 
downside is that you have to sort out the storage checkpointing you want ;-p  
As a result I'm not sure that it's actually that usable for now although the 
existence of the functionality is cool and you could certainly set up some 
interesting stuff with it.

When playing with this stuff, do be a bit careful.  It's easy to corrupt disk 
images by messing around with suspend/resume in unexpected ways.  For 
instance, if you checkpoint a domain, let it run for a bit, then destroy the 
running copy and restore the checkpoint.  The resumed domain will try and 
write to the disk, but it'll have a completely different idea of what should 
be on the disk.  This is very likely to result in damage to or loss of the 
filesystem.

Ideally, when you checkpoint the guest you'd also checkpoint the storage.  
Then if you resume the checkpoint of the guest's runtime state, you could 
first copy the backup of the storage into place.  ISTR that if you checkpoint 
a paused domain, it'll do the checkpoint and then repause the domain - at 
this point you'd be able to backup the storage and then unpause.  This would 
allow you to create a complete and consistent backup of a running domain.

Cheers,
Mark

On Monday 28 April 2008, Ian Brown wrote:
> Hello,
>   I have xen-3.1.0-13.fc8 on Fedora Core 8.
> This version supports checkpointing for "xm save" command.
>

Re: Newbie Question on Comparisons/Advice

> I've read (have not done comparisons for myself) that a loopback-mounted
> file in a Linux system will give comparable performance to a raw device
> (i.e. LVM volume).  The advantage of LVM is in the flexibility, but
> you're in a situation where the up-front costs (shrinking filesystem,
> spending some time with the LVM docs) might outweigh the advantages.

LVM is generally recommended for Xen guest storage for reasons of performance, 
flexibility and robustness.  Basically, it's about as fast as using raw disk 
but with the flexibility of being able to easily resize, snapshot, etc.  
Using files was sort-of not recommended for production environments since the 
Linux loopback device has some limitations (performance, scalability and 
flexibility, I think)

I've found that loopback devices are perfectly adequate for playing around 
with stuff on a small system, however.  Also, using tap:aio: instead of file: 
allows you to make a regular Linux file available as a VBD without the 
problems of the block loopback.  I think that's the recommended way to do 
things these days.

> If you want to do it that way, yeah, you'll need to shrink the
> filesystem, then you'll need to shrink the (virtual) device it lives on,
> and then you can create a new virtual device in the freed space.  But
> it's quicker just to dd a bunch of zeroes into a file and treat that as
> a disk.

Indeed!

> > This now brings me back to having to start over reinstalling Fedora;
> > from my understanding.
>

Re: Fwd: Dinamically allocated memory in a virtual machine

Hi Madrivi,

> Hello, i have been looking for some info about how to expand dinamically
> the memory of my virtual machines, can someone give me a tip please?

Sure.

>  I have basic skills with the xen world, just now  iam only able to create
> virtual machines from a template, manage them a little with xen tools, and
> i don't know how to manage dinamically this settings, memory, disk space of
> the virtual machine etc, when the machines are running.
>
> Is even possible, or can't be done?

The "xm mem-set" command can be used to resize the memory a domain is using.  
You can use it to shrink the domain's memory or to grow it again.

The "xm mem-max" command is used to set the maximum memory a domain is allowed 
to have.

Note that ordinarily XenLinux does not support being grown beyond its initial 
a location of RAM.  If you want to be able to do this, you need to add 
something like mem=4G (for a maximum of 4G) to the domain's kernel command 
line in order to tell it how big it might get.  This is so the guest Linux 
can size its tables to fit the amount of memory.

The above refers to paravirtualised (PV) domains.  If you install a PV driver 
kit you should be able to resize the memory of a fully virtualised (HVM) 
domain but I don't think it can grow beyond its initial size.

Re: Creating a RHELGuest VM

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What's recommended method for serving data to/among DomU's?

I'm looking for comments/opinions on the pros & cons of various ways
of serving data to DomU's ...

Given a number of DomU VM's on a given box, data sotrage can take several forms:

 (1) Data served via NFS from Dom0 to DomU
 (2) Data served from a DomU-dedicated NAS, e.g., via NFS, OpenFiler, etc
 (3) Data stored locally in each DomU

The options above vary, at least, in security, performance, and backup strategy.

I'm interested in what folks here recommend.

Thanks!

testing

Testing list, haven't received email since this morning.

Re: Release 0.8.9 of GPL PV drivers for Windows

Michele Castigliego schrieb:
> Hi guys,
> I've done a Windos ITA fresh install under Xen in a non production
> envirement and installed the GPL PV drivers. Now I have duplicated
> (working) entries in my hardware list, but I think it's not correct..
> 
> If you are interested I can tell what I've done:
> 
> 1. Install a Debian Etch + xen stable + quemu (I don't think it's really
> relevant)
> 2. Install Windows XP SP2 ITA under xen without (in)security updates
> from Bill at the moment
> 3. Downloaded and extracted 0.8.9 GPL PV drivers
> 4. Launched install.bat (I didn't build anything, is it correct?)
> 4a. It showed me a console which tells: Windows XP detected... Install..
>     and a ShotdownMon.exe error message:
>     Application error 0xc0000135 -> OK to close.

This error occurs if the Microsoft.NET Framework 2.0 is not installed.
shutdownmon needs this framework, the drivers itself should work without
it.

>     Then all goes as expected.
> 5. Finally I've rebooted non gplpv, founded new hardware, changed
> boot.ini, rebooted gplpv, and founded duplicated entries..
> 
> Now I have two CDs, one QEMU and one XEN PV Scsi,  both working, two
> network cards, same as above, two HD controllers but the HD is on the
> old QEMU's one..

This is an often reported bug, AFAIK there is no real solution. In this
situation you're at high risk of corrupting your domU filesystem. You
shouldn't boot /gplpv if this occurs. I think it has to do with some
xen / qemu-dm device namespace as it depends which version of xen you're
running. It looks like internationalized versions of windows are hit more
often by this bug.

> I've disabled the Realtek NIC by hand and still have networking throw
> XEN PV.

To use xen pv nic's, I've always changed the vif =[...] from type=ioemu
to type=netfront and changed the mac address as i found windows getting
confused by different nic's with the same mac.

> 
> If there is something more I can tell you, ask.
> 
> Mic
> 	
> 
> 
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