[Discuss] LVM vs File system file for KVM Virtual Machines?

[derek at ihtfp.com (Derek Atkins)]

Mark,

Think about it this way:  when using a file on the file system the VM has
a whole extra layer of indirection that it has to go through, because it
has to go through the FS layer in the VM, then the block layer in the VM,
then the VM system storage layer, and then the FS layer in the host, then
block layer in the host..   Whereas if it's just an LVM container then you
can bypass the FS layer in the host completely.  So I would always expect
the direct LVM container to be faster and more resource efficient.

-derek

On Thu, March 29, 2012 10:49 am, markw at mohawksoft.com wrote:
> Hopefully without getting into an augment about the pros and cons of LVM
> vs btrfs or zfs, does anyone want to discuss the pros and cons of LVM
> "device" for a virtual machine vs a file on a file system for a virtual
> machine?
>
> So, do you create a 30G file on a file system, like EXT3, jfs, or xfs and
> use that or do you create a 30G LVM device and use it directly? There are
> some benefits to using LVM and with the 3.x kernel, you could even use a
> "thin provisioned" device.
>
> Which do you suspect would be more resource efficient? Which do you think
> would have faster I/O?
>
> I've set up two systems, one on a jfs file system and one on an "old
> style" LVM partition. (Fully allocated). I don't see much of a difference.
> I suspect the LVM based system should be more efficient because it does
> not have to go through the intermediate file system layer to get to the
> device layer. Internally, the VM sees the LVM device as its own device.
>
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>


-- 
       Derek Atkins                 617-623-3745
       derek at ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant