[ovirt-users] Reclaim disk space of thin disks

[Yaniv Kaul]

On Thu, Mar 31, 2016 at 1:16 PM, Grundmann, Christian <
Christian.Grundmann at fabasoft.com> wrote:

> Hi,
>
> @1. Did you use the hook?
>
> yes, without the hook fstrim would not start,
>
> @2. Where did you see it's the same size? Should be looked at from the
> storage side (assuming, btw, it supports discard!)
>
> I looked at the “actual Size” under Storage
>

I'm unsure if that size should change - we've allocated blocks, they are
still allocated from our perspective. From the storage point of view,
there's a hole that can be used for other purposes.
I'd look on the storage side.

>
>
> I don’t know how ovirt handles FC storage and if this will allow discard.
>

It doesn't really care - thee discard should be passed to the underlying
storage. Most should support UNMAP these days. But you can easily check, I
assume with a small test (use sg3_utils for example).
Y.


>
> Thx
>
> Christian
>
>
>
>
>
> *Von:* Yaniv Kaul [mailto:ykaul at redhat.com]
> *Gesendet:* Donnerstag, 31. März 2016 12:13
>
> *An:* Grundmann, Christian <Christian.Grundmann at fabasoft.com>
> *Cc:* users at ovirt.org
> *Betreff:* Re: [ovirt-users] Reclaim disk space of thin disks
>
>
>
>
>
>
>
> On Thu, Mar 31, 2016 at 1:05 PM, Grundmann, Christian <
> Christian.Grundmann at fabasoft.com> wrote:
>
> Hi,
>
> seems not to work with FC Storage,
>
>
>
> I Zero filled the Disk with dd, removed the file and did a fstrim which
> told me it trimmed the right amount of space,
>
> But the disk Image stays full size.
>
>
>
> 1. Did you use the hook?
>
> 2. Where did you see it's the same size? Should be looked at from the
> storage side (assuming, btw, it supports discard!)
>
> Y.
>
>
>
>
>
> Thx
>
> Christian
>
>
>
> *Von:* Yaniv Kaul [mailto:ykaul at redhat.com]
> *Gesendet:* Mittwoch, 30. März 2016 22:29
> *An:* Grundmann, Christian <Christian.Grundmann at fabasoft.com>
> *Cc:* users at ovirt.org
> *Betreff:* Re: [ovirt-users] Reclaim disk space of thin disks
>
>
>
>
>
>
>
> On Wed, Mar 30, 2016 at 10:04 AM, Grundmann, Christian <
> Christian.Grundmann at fabasoft.com> wrote:
>
> Hi,
>
> is there a way to „shrink“ a thin disk image to reclaim deleted space like
> using virt-sparsify?
>
>
>
> Yes, if the underlying file system supports it (NFS, for example, might
> need to be 4.2 and above).
>
>
>
> Or can it be done by making a snapshot and clone the VM to a new one?
>
>
>
> Another suggestion: use the VDSM hooks for discard ('diskunmap') and run
> 'fstrim' from within the guest.
>
> Y.
>
>
>
>
>
> Thanks a lot
>
> Christian
>
>
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