Open Stack

On Tue, Mar 4, 2014 at 1:06 AM, Qin Zhao <chaochin at gmail.com> wrote:
> I think the current snapshot implementation can be a solution sometimes, but
> it is NOT exact same as user's expectation. For example, a new blueprint is
> created last week,
> https://blueprints.launchpad.net/nova/+spec/driver-specific-snapshot, which
> seems a little similar with this discussion. I feel the user is requesting
> Nova to create in-place snapshot (not a new image), in order to revert the
> instance to a certain state. This capability should be very useful when
> testing new software or system settings. It seems a short-term temporary
> snapshot associated with a running instance for Nova. Creating a new
> instance is not that convenient, and may be not feasible for the user,
> especially if he or she is using public cloud.
>

Why isn't it easy to create a new instance from a snapshot?

>
> On Tue, Mar 4, 2014 at 1:32 PM, Nandavar, Divakar Padiyar
> <divakar.padiyar-nandavar at hp.com> wrote:
>>
>> >>> Why reboot an instance? What is wrong with deleting it and create a
>> >>> new one?
>>
>> You generally use non-persistent disk mode when you are testing new
>> software or experimenting with settings.   If something goes wrong just
>> reboot and you are back to clean state and start over again.    I feel it's
>> convenient to handle this with just a reboot rather than recreating the
>> instance.
>>
>> Thanks,
>> Divakar
>>
>> -----Original Message-----
>> From: Joe Gordon [mailto:joe.gordon0 at gmail.com]
>> Sent: Tuesday, March 04, 2014 10:41 AM
>> To: OpenStack Development Mailing List (not for usage questions)
>> Subject: Re: [openstack-dev] [nova][cinder] non-persistent storage(after
>> stopping VM, data will be rollback automatically), do you think we shoud
>> introduce this feature?
>> Importance: High
>>
>> On Mon, Mar 3, 2014 at 8:13 PM, Zhangleiqiang <zhangleiqiang at huawei.com>
>> wrote:
>> >>
>> >> This sounds like ephemeral storage plus snapshots.  You build a base
>> >> image, snapshot it then boot from the snapshot.
>> >
>> >
>> > Non-persistent storage/disk is useful for sandbox-like environment, and
>> > this feature has already exists in VMWare ESX from version 4.1. The
>> > implementation of ESX is the same as what you said, boot from snapshot of
>> > the disk/volume, but it will also *automatically* delete the transient
>> > snapshot after the instance reboots or shutdowns. I think the whole
>> > procedure may be controlled by OpenStack other than user's manual
>> > operations.
>>
>> Why reboot an instance? What is wrong with deleting it and create a new
>> one?
>>
>> >
>> > As far as I know, libvirt already defines the corresponding <transient>
>> > element in domain xml for non-persistent disk ( [1] ), but it cannot specify
>> > the location of the transient snapshot. Although qemu-kvm has provided
>> > support for this feature by the "-snapshot" command argument, which will
>> > create the transient snapshot under /tmp directory, the qemu driver of
>> > libvirt don't support <transient> element currently.
>> >
>> > I think the steps of creating and deleting transient snapshot may be
>> > better to done by Nova/Cinder other than waiting for the <transient> support
>> > added to libvirt, as the location of transient snapshot should specified by
>> > Nova.
>> >
>> >
>> > [1] http://libvirt.org/formatdomain.html#elementsDisks
>> > ----------
>> > zhangleiqiang
>> >
>> > Best Regards
>> >
>> >
>> >> -----Original Message-----
>> >> From: Joe Gordon [mailto:joe.gordon0 at gmail.com]
>> >> Sent: Tuesday, March 04, 2014 11:26 AM
>> >> To: OpenStack Development Mailing List (not for usage questions)
>> >> Cc: Luohao (brian)
>> >> Subject: Re: [openstack-dev] [nova][cinder] non-persistent
>> >> storage(after stopping VM, data will be rollback automatically), do
>> >> you think we shoud introduce this feature?
>> >>
>> >> On Mon, Mar 3, 2014 at 6:00 PM, Yuzhou (C) <vitas.yuzhou at huawei.com>
>> >> wrote:
>> >> > Hi stackers,
>> >> >
>> >> > As far as I know ,there are two types of storage used by VM in
>> >> > openstack:
>> >> Ephemeral Storage and Persistent Storage.
>> >> > Data on ephemeral storage ceases to exist when the instance it is
>> >> > associated
>> >> with is terminated. Rebooting the VM or restarting the host server,
>> >> however, will not destroy ephemeral data.
>> >> > Persistent storage means that the storage resource outlives any
>> >> > other
>> >> resource and is always available, regardless of the state of a running
>> >> instance.
>> >> >
>> >> > There is a use case that maybe need a new type of storage, maybe we
>> >> > can
>> >> call it non-persistent storage .
>> >> > The use case is that VMs are assigned to the public ephemerally in
>> >> > public
>> >> areas.
>> >> > After the VM is used, new data on storage of VM ceases to exist
>> >> > when the
>> >> instance it is associated with is stopped.
>> >> > It means stop the VM, Non-persistent storage used by VM will be
>> >> > rollback
>> >> automatically.
>> >> >
>> >> > Is there any other suggestions? Or any BPs about this use case?
>> >> >
>> >>
>> >> This sounds like ephemeral storage plus snapshots.  You build a base
>> >> image, snapshot it then boot from the snapshot.
>> >>
>> >> > Thanks!
>> >> >
>> >> > Zhou Yu
>> >> >
>> >> > _______________________________________________
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>> >> > OpenStack-dev at lists.openstack.org
>> >> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>> >>
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>
>
>
> --
> Qin Zhao
>
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