Open Stack

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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>>
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