Re: [Xen-users] xvda vs lvm

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> 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.

> 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

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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