* [Qemu-devel] snapshot vs COW?
@ 2008-12-12 3:17 Jun Koi
2008-12-12 3:18 ` [Qemu-devel] " Jun Koi
2008-12-12 13:25 ` walt
0 siblings, 2 replies; 6+ messages in thread
From: Jun Koi @ 2008-12-12 3:17 UTC (permalink / raw)
To: qemu-devel
Hi,
>From what I see, both snapshot and COW features can be used to try
some changes on the file image before we the change back to the
original image.
But what is the advantages of snapshot over COW, and in which case we
should use snapshot, but not COW? Vice verse, when COW is more
appropriate?
Many thanks,
Jun
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Qemu-devel] Re: snapshot vs COW?
2008-12-12 3:17 [Qemu-devel] snapshot vs COW? Jun Koi
@ 2008-12-12 3:18 ` Jun Koi
2008-12-12 13:25 ` walt
1 sibling, 0 replies; 6+ messages in thread
From: Jun Koi @ 2008-12-12 3:18 UTC (permalink / raw)
To: qemu-devel
On Fri, Dec 12, 2008 at 12:17 PM, Jun Koi <junkoi2004@gmail.com> wrote:
> Hi,
>
> From what I see, both snapshot and COW features can be used to try
> some changes on the file image before we the change back to the
> original image.
I mean "... before we merge then changes back ..."
Thanks,
Jun
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Qemu-devel] Re: snapshot vs COW?
2008-12-12 3:17 [Qemu-devel] snapshot vs COW? Jun Koi
2008-12-12 3:18 ` [Qemu-devel] " Jun Koi
@ 2008-12-12 13:25 ` walt
2008-12-14 18:12 ` Jamie Lokier
1 sibling, 1 reply; 6+ messages in thread
From: walt @ 2008-12-12 13:25 UTC (permalink / raw)
To: qemu-devel
Jun Koi wrote:
> Hi,
>
> From what I see, both snapshot and COW features can be used to try
> some changes on the file image before we the change back to the
> original image.
>
> But what is the advantages of snapshot over COW, and in which case we
> should use snapshot, but not COW? Vice verse, when COW is more
> appropriate?
>
> Many thanks,
> Jun
COW is a nice feature but it is currently broken, so don't use it
until it gets fixed. When you commit any changes your backing file
will be corrupted.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] Re: snapshot vs COW?
2008-12-12 13:25 ` walt
@ 2008-12-14 18:12 ` Jamie Lokier
2008-12-14 18:35 ` Thiemo Seufer
0 siblings, 1 reply; 6+ messages in thread
From: Jamie Lokier @ 2008-12-14 18:12 UTC (permalink / raw)
To: qemu-devel
walt wrote:
> Jun Koi wrote:
> >Hi,
> >
> > From what I see, both snapshot and COW features can be used to try
> >some changes on the file image before we the change back to the
> >original image.
> >
> >But what is the advantages of snapshot over COW, and in which case we
> >should use snapshot, but not COW? Vice verse, when COW is more
> >appropriate?
> >
> >Many thanks,
> >Jun
>
> COW is a nice feature but it is currently broken, so don't use it
> until it gets fixed. When you commit any changes your backing file
> will be corrupted.
Aieee! I use COW instead of snapshots in my management scripts,
because snapshots are harder to manage.
Is the COW brokenness documented? What version did it start being broken?
-- Jamie
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] Re: snapshot vs COW?
2008-12-14 18:12 ` Jamie Lokier
@ 2008-12-14 18:35 ` Thiemo Seufer
2008-12-14 22:07 ` walt
0 siblings, 1 reply; 6+ messages in thread
From: Thiemo Seufer @ 2008-12-14 18:35 UTC (permalink / raw)
To: Jamie Lokier; +Cc: qemu-devel
Jamie Lokier wrote:
> walt wrote:
> > Jun Koi wrote:
> > >Hi,
> > >
> > > From what I see, both snapshot and COW features can be used to try
> > >some changes on the file image before we the change back to the
> > >original image.
> > >
> > >But what is the advantages of snapshot over COW, and in which case we
> > >should use snapshot, but not COW? Vice verse, when COW is more
> > >appropriate?
> > >
> > >Many thanks,
> > >Jun
> >
> > COW is a nice feature but it is currently broken, so don't use it
> > until it gets fixed. When you commit any changes your backing file
> > will be corrupted.
>
> Aieee! I use COW instead of snapshots in my management scripts,
> because snapshots are harder to manage.
>
> Is the COW brokenness documented? What version did it start being broken?
Cow2 is broken in the 0.9.1 release, it was fixed shortly afterwards.
The symptom was corruption of the image when it grew beyond 4 GB.
AFAIK you can still break cow2 images by running out of disk space.
This is the case since cow2 suport was written.
Thiemo
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Qemu-devel] Re: snapshot vs COW?
2008-12-14 18:35 ` Thiemo Seufer
@ 2008-12-14 22:07 ` walt
0 siblings, 0 replies; 6+ messages in thread
From: walt @ 2008-12-14 22:07 UTC (permalink / raw)
To: qemu-devel
Thiemo Seufer wrote:
> Jamie Lokier wrote:
>> walt wrote:
>>> COW is a nice feature but it is currently broken, so don't use it
>>> until it gets fixed. When you commit any changes your backing file
>>> will be corrupted.
>> Aieee! I use COW instead of snapshots in my management scripts,
>> because snapshots are harder to manage.
>>
>> Is the COW brokenness documented? What version did it start being broken?
> Cow2 is broken in the 0.9.1 release, it was fixed shortly afterwards.
> The symptom was corruption of the image when it grew beyond 4 GB...
Glad to hear it, thanks for the update. That means that the fix is
already in the kvm git repository?
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2008-12-14 22:07 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2008-12-12 3:17 [Qemu-devel] snapshot vs COW? Jun Koi
2008-12-12 3:18 ` [Qemu-devel] " Jun Koi
2008-12-12 13:25 ` walt
2008-12-14 18:12 ` Jamie Lokier
2008-12-14 18:35 ` Thiemo Seufer
2008-12-14 22:07 ` walt
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