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From John Burwell <>
Subject Re: S3-backed Secondary Storage Enhancement
Date Mon, 03 Dec 2012 15:25:42 GMT

Please see my responses in-line below.


On Nov 20, 2012, at 9:33 PM, Chiradeep Vittal <> wrote:

> I must give kudos on the document
> (
> +Storage ). Quite complete
> If the intent is to make immutable assets (templates etc) visible across
> all zones:
> 1. Does the template_zone_ref table still make sense? Is it automatically
> updated?

Yes, the template_zone_ref table is still required.  Templates and ISOs must be attached to
a zone.  From my understanding of the system design, removing this requirement would require
a fundamental data model/architectural change.  Therefore, cross zone templates are supported
by creating a row in the template_zone_ref table associating the template to the zone.  These
propigation operations are performed upon template and zone creation.  This behavior pre-dates
this patch.  This patch automates the operation of propagating the data across zones.

I have updated the data model section of the design document to describe the data flow and
role of each table.

> 2. If I request a vm deployment from a template in a zone that has not yet
> sync'ed, what is the behavior?

The short answer is that S3 download behaves similarly to Swift downloads.  Templates and
ISOs are downloaded from S3 to NFS on-demand.  When a template is not found in the NFS volume,
the system will attempt to downloaded it from S3.  As noted in the design download, this on-demand
behavior may create a slight lag when a template is initially accessed in a zone dependent
on the available bandwidth between the SSVM and the S3-compatible store.

> 3. If I add a zone is the sync automatic to the new zone

Yes, per the template propagation and on-demand download behaviors described above, templates
and ISOs will automatically be available in a newly created zones.

I explained this process in the Architecture/Design section, and have updated it based on
on my response here.  Please let me know if it is needs further clarification.

> On 11/18/12 10:51 PM, "John Burwell" <> wrote:
>> All,
>> I have submitted the initial revision of a patch to support S3 backing
>> NFS secondary storage (  I have
>> opened ticket CLOUDSTACK-509 to track the testing and delivery of the
>> enhancement.  I have also created a design document in the wiki roughly
>> following design document template.  Since I am not a committer, it did
>> not seem appropriate for me to add a reference from the roadmap to the
>> ticket.  
>> In its current state, I have tested the single zone template and ISO
>> functionality on devcloud.  I am working to configure a multi-zone
>> integration testing environment to complete all test scenarios outlined
>> in the design document.  My plan is to refine the arch per community
>> patch concurrently with the completion of integration testing and bug
>> squashing.
>> I look forward to your feedback,
>> -John

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