Re: [Xen-users] xvda vs lvm

[tarjei <tarjei@xxxxx>]

Hi,
Mark Williamson wrote:
> > Hi, I'm just wondering if there are any speed or stability differences
> > between running a system directly of a LVM partition versus a xvd
> > partition?
> >
> > I'm a little confused about what you're asking, so I'll explain a few things 
> > and hopefully it'll help some.  Please ask again if I'm not answering the 
> > questions you wanted.
> >     
I was mainly wondering about the speed issues involved in the two 
approaches. Since I didn't hear anything the first few days, I also 
asked on #xen where I was told that there isn't any performance overhead 
and that overloading the normal disk, say /dev/hda1, will be phased out 
in the future.
Thank you for your answer.

Kind regards,
Tarjei

> > Basicly:
> > disk = [ 'phy:/dev/LVM/root,xvda,w', ]
> >     
> This exports /dev/LVM/root as the whole disk device /dev/xvda in the guest.
>
>   
> > disk= [ 'phy:LVM/root,hda1,w',]
> >     
> This exports /dev/LVM/root (as before) as the partition /dev/hda1 in the 
> guest.
> So, whether or not you include /dev in the device path, you're still exporting 
> the same device.
> As to whether to export a whole device or a partition...
>
> Exporting as a single partition (e.g. /dev/hda1 in your example) has the 
> advantage that /dev/LVM/root will be directly mountable in dom0 because it 
> will not have been partitioned by the guest.  The guest won't be allowed to 
> repartition /dev/hda, it'll be stuck with one partition there.
> Exporting as a whole device gives the guest flexibility to partition its VBD 
> as it sees fit but means it's slightly less convenient to mount /dev/LVM/root 
> in dom0 (but there are tools to read the partition and make this easy for 
> you).
> I usually go for the latter approach, but it doesn't matter in terms of speed 
> and stability.  It's really quest a question of administration convenience 
> and how you want things to look like the guest.
> Cheers,
> Mark
>
>   

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