[rhelv6-list] How can I create sparse block devices as a logical volumes with lvm

[Benjamin Franz]

On 02/04/2011 03:37 AM, John Haxby wrote:
>
>
> On 4 February 2011 08:50, carlopmart <carlopmart at gmail.com 
> <mailto:carlopmart at gmail.com>> wrote:
>
>     Hi all,
>
>      Is it possible to create sparse block devices with LVM (logical
>     volumes not volume groups) on RHEL6 like ZFS does??
>
>
> Do you mean something like this (from the lvcreate man page):
>
>         "lvcreate --virtualsize 1T --size 100M --snapshot --name 
> sparse vg1"
>        creates a sparse device named /dev/vg1/sparse of size  1TB  
> with  space
>        for just under 100MB of actual data on it.
>

Ok. Cool feature from a technical perspective....But...What is the use 
case? I'm trying to wrap my head over why I would want to overcommit a 
logical volume's usable storage. I'm assuming there is some use case 
where it makes sense, but I'm not seeing it.
The closest I can come is that you might manually resize the lv's 'real' 
size if you ever got close to filling it up.

Enlighten me?

-- 
Benjamin Franz
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