Does your application depend on, or report, free disk space? Re: F20 Self Contained Change: OS Installer Support for LVM Thin Provisioning

[Chris Murphy]

On Jul 26, 2013, at 3:02 PM, drago01 <drago01 at gmail.com> wrote:

> On Fri, Jul 26, 2013 at 10:59 PM, Miloslav Trmač <mitr at volny.cz> wrote:
>> On Fri, Jul 26, 2013 at 10:17 PM, DJ Delorie <dj at redhat.com> wrote:
>>> 
>>>> If your package reports disk space usage to users, and bases this on
>>>> filesystem free space, please consider whether it might need to take
>>>> LVM thin provisioning into account.
>>> 
>>> Perhaps you could include a small code snippet explaining *how* to do
>>> this?  Is there an lvm_thin_statfs() we can use?
>> 
>> I'd love to, but I don't know how.  David, could you suggest something, please?
> 
> The same issue exits for btrfs ... shouldn't we somehow try to get a
> generic api for the "exotic" file systems?

I don't think btrfs yet supports thin provisioning itself via quotas. The quotas code is still in flux in any case. I have had some problems with lvm thinp and btrfs that happen more rarely with xfs. The thinp LV is somewhat large, 16TB for the available RAM on the machine, 4GB. But I don't have the same problems when using qcow2 to thin provision the same amount of space.

But isn't the idea that the file system itself isn't really aware of how much actual space is available? That's up to the manager of the thin provisioned space, in this case LVM. Not the file system.


Chris Murphy