[linux-lvm] thin handling of available space

[Gionatan Danti]

On 03/05/2016 13:42, Zdenek Kabelac wrote:
>
> Danger with having 'disable' options like this is many distros do decide
> themselves about best defaults for their users, but Ubuntu with their
> issue_discards=1 shown us to be more careful as then it's not Ubuntu but
> lvm2 which is blamed for dataloss.
>
> Options are evaluated...
>

Very true. "Sane defaults" is one of the reason why I (happily) use 
RHEL/CentOS as hypervisors and other critical tasks.

>
>
> What's wrong with  'lvs'?
> This will give you the available space in thin-pool.
>

Oh, absolutely nothing wrong with lvs. I used "lsblk" only as an example 
of the block device/layer exposing some (lack of) features to upper layer.

One note about the continued "suggestion" to use BTRFS. While for 
relatively simple use case it can be ok, for more demanding 
(rewrite-heavy) scenarios (eg: hypervisor, database, ecc) it performs 
*really* bad, even when "nocow" is enabled.

I had much more fortune, performance wise, with ZFS. Too bad ZoL is an 
out-of-tree component (albeit very easy to install and, in my 
experience, quite stable also).

Anyway, ThinLVM + XFS is an extremely good combo in my opinion.

>
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 
Danti Gionatan
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