Re: [Xen-users] why LVM? why not Extended Partitions?

[Tomasz Chmielewski <mangoo@xxxxxxxx>]

Emre Erenoglu schrieb:
> Hi,
>
> This is for HVM guests.
>
> I'm using LVM at my home setup for my DomUs, but having some issues with 
> "mounting, umounting" the partitions inside the DomUs, as they are 
> actually a disk image. Some of the kernels of my DomU's don't have LVM 
> support at all, making it another issue.
> Why don't we just use Extended Partitions? What is the added benefit of 
> LVM to us? I read around that it also includes a little overhead. When 
> it comes to extension, shringking, modification etc, extended partitions 
> are just as good, as you can use many proved commercial products to 
> resize your partitions easily.
> Am I missing something here?
Yes, in several points.

1. It's dom0 which needs LVM support; domUs don't need it. In fact, 
whatever you use on dom0 as a storage for domU (LVM, disk, partition, 
file etc.) doesn't matter from the domU point of view - in the end, domU 
sees "a disk" anyway.
2. How many partitions can you have with extended partitions? I think 
it's 16 maximum. I also think there is a maximum size (1 or 8 TB, I 
don't remember) old-style partitioning can handle.
But I guess it won't matter for smaller setups anyway.

Let's consider you have 3 partitions with different size, and some free 
space after them:
[ A     ][ B   ][ C       ][ free     ]

You find that partition B is too small, and you want to resize it? Super 
easy with LVM, and lots of effort when using old-style partitions.
Still LVM not fun for you? It has some additional goodies (like 
snapshots, etc.).

--
Tomasz Chmielewski
http://wpkg.org


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