Re: Possible to use multiple disk to bypass I/O wait?

[Gordon Messmer <yinyang@xxxxxxxxx>]

On 06/15/2011 07:04 PM, Emmanuel Noobadmin wrote:
> Looking at some very sparse notes I made on the decision, I think what
> tipped the choice was that both qcow2 and lvm added overheads, but lvm
> was on the whole system i.e. the host has additional processing on
> every i/o whereas qcow2 overheads was only for guest i/o.

I think you were misinformed, or misled.  LVM should not present any 
noticeable overhead on the host.  Using "raw" files to back VMs presents 
a significant overhead to guests; the host performs all IO through its 
filesystem.  Using "qcow2" files presents even more overhead (probably 
the most of any configuration) since there are complexities to the qcow2 
file itself in addition to the host's filesystem.

> More
> critically my note was the thought as well that it would be easier to
> move a qcow2 file to another machine/disk if necessary than to move a
> partition.

It shouldn't be significantly harder to copy the contents of a partition 
or LV.  The block device is a file.  You can read its contents to copy 
them just as easily as any other file.
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