[openstack-dev] [nova][cinder] non-persistent storage(after stopping VM, data will be rollback automatically), do you think we shoud introduce this feature?

Yuzhou (C) vitas.yuzhou at huawei.com
Mon Mar 17 11:34:58 UTC 2014

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.


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!


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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