[openstack-dev] [nova][cinder] non-persistent storage(after stopping VM, data will be rollback automatically), do you think we shoud introduce this feature?
zhangleiqiang at huawei.com
Tue Mar 18 03:32:09 UTC 2014
> From: Vishvananda Ishaya [mailto:vishvananda at gmail.com]
> Sent: Tuesday, March 18, 2014 2:28 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?
> On Mar 17, 2014, at 4:34 AM, Yuzhou (C) <vitas.yuzhou at huawei.com> wrote:
> > Hi Duncan Thomas,
> > Maybe the statement about approval process is not very exact. In fact in
> my mail, I mean:
> > In the enterprise private cloud, if beyond the quota, you want to create a new
> VM ,that needs to wait for approval process.
> > @stackers,
> > I think the following two use cases show why non-persistent disk is useful:
> > 1.Non-persistent VDI:
> > When users access a non-persistent desktop, none of their settings or
> data is saved once they log out. At the end of a session,
> > the desktop reverts back to its original state and the user receives a fresh
> image the next time he logs in.
> > 1). Image manageability, Since non-persistent desktops are built from a
> master image, it's easier for administrators to patch and update the image,
> back it up quickly and deploy company-wide applications to all end users.
> > 2). Greater security, Users can't alter desktop settings or install their own
> applications, making the image more secure.
> > 3). Less storage.
> > 2.As the use case mentioned several days ago by zhangleiqiang:
> > "Let's take a virtual machine which hosts a web service, but it is primarily
> a read-only web site with content that rarely changes. This VM has three disks.
> Disk 1 contains the Guest OS and web application (e.g. Apache). Disk 2
> contains the web pages for the web site. Disk 3 contains all the logging activity.
> > In this case, disk 1 (OS & app) are dependent (default) settings and
> is backed up nightly. Disk 2 is independent non-persistent (not backed up, and
> any changes to these pages will be discarded). Disk 3 is independent
> persistent (not backed up, but any changes are persisted to the disk).
> > If updates are needed to the web site's pages, disk 2 must be
> taken out of independent non-persistent mode temporarily to allow the
> changes to be made.
> > Now let's say that this site gets hacked, and the pages are
> doctored with something which is not very nice. A simple reboot of this host will
> discard the changes made to the web pages on disk 2, but will persist the
> logs on disk 3 so that a root cause analysis can be carried out."
> > Hope to get more suggestions about non-persistent disk!
> Making the disk rollback on reboot seems like an unexpected side-effect we
> should avoid. Rolling back the system to a known state is a useful feature, but
> this should be an explicit api command, not a side-effect of rebooting the
> machine, IMHO.
I think there is some misunderstanding about non-persistent disk, the non-persistent disk will only rollback if the instance is shutdown and start again, and will persistent the data if it is soft-reboot.
Non-persistent disk does have use cases. Using explicit API command can achieve it, but I think there will be some work need to be done before booting the instance or after shutdown the instance, including:
1. For cinder volume, create a snapshot; For libvirt ephemeral image backend, create new image
2.Update attached volume info for instance
3.Delete the cinder snapshot and libvirt ephemeral image, and update volume/image info for instance again
These works can be done by users manually or by some "Upper system" ? Or non-persistent can be set as a metadata/property of volume/image, and handled by Nova?
> > Thanks.
> > Zhou Yu
> >> -----Original Message-----
> >> From: Duncan Thomas [mailto:duncan.thomas at gmail.com]
> >> Sent: Saturday, March 15, 2014 12:56 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?
> >> On 7 March 2014 08:17, Yuzhou (C) <vitas.yuzhou at huawei.com> wrote:
> >>> First, generally, in public or private cloud, the end users
> >>> of VMs
> >> have no right to create new VMs directly.
> >>> If someone want to create new VMs, he or she need to wait for
> >>> approval
> >> process.
> >>> Then, the administrator Of cloud create a new VM to applicant. So
> >>> the
> >> workflow that you suggested is not convenient.
> >> This approval process & admin action is the exact opposite to what
> >> cloud is all about. I'd suggest that anybody using such a process has
> >> little understanding of cloud and should be educated, not weird
> >> interfaces added to nova to support a broken premise. The cloud /is
> >> different/ from traditional IT, that is its strength, and we should
> >> be wary of undermining that to allow old-style thinking to continue.
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