[glue-wg] Extending GLUE 2.0 for Cloud services

Tue Nov 5 11:46:13 EST 2013

Hi all,

I had no time to read the document yet, but here's some comments at a
first glance on these proposed changes.

On 2013-11-05 13:49, Salvatore Pinto wrote:
> Hi Stephen,
> yes, replacing "files" with "data object" in the text it is fine, but,
> in my opinion, we should also perform the following changes:
>
> * Add to StorageEndpoint element the following attribute:
>
> SupportedObjects
>
> 	
>
> CloudStorageT_t
>
> 	
>
> *
>
> 	
>
>  
>
> 	
>
> Supported data object formats (ex. Image disks, files, generic
> objects, etc…)
>
> . For the use is important to know which kind of storage the service
> provides, if it is storage for files, disk images, EBS attached
> storage, etc...

It's bad design to add one more attribute for this purpose I think. The
question "what kind of storage is provided" should be answered by
looking at
capabilities. I think capabilities are the key thing to know "what a
service does" or "what an endpoint does". Moreover, since they are open
enumerations, one can use all his/her fantasy to make them mean whatever
they're targeted, and it's very much extensible.

Examples:
data.management.diskimage
data.management.file
data.management.genericobject

if you don't like 'management' you can change it to some other thing,
but I feel it fits...
something like 'data.supportedobject.diskimage'

> * Add to StorageShare the following attributes:
>
> MaxObjectSize
>
> 	
>
> UInt64
>
> 	
>
> 0..1
>
> 	
>
> MB
>
> 	
>
> Maximum size of a data object who can be stored in this share
>
> MinObjectSize
>
> 	
>
> UInt64
>
> 	
>
> 0..1
>
> 	
>
> MB
>
> 	
>
> Minimum size of a data object who can be stored in this share
>
> This is very important for the user (especially for EBS storage, where
> the storage object is a disk attached to a VM) to choose which storage
> service is better for their need and for the authomatic systems to
> perform auto-scaling of the storage.
>
I can see the benefit of these attributes. However, maybe the best place
where to put these two attributes is StorageShareCapacity and not
StorageShare.

Cheers,
Florido

> Of course, we could use the extensions to add these attributes and do
> not change the standard...
>

I think you can use Extensions until we change the standard :) but since
you devise these will be extensively used in clouds,
I see no problem changing the standard.

> Regarding the capabilities for the storage taken from CDMI or other
> cloud standards (ex. support for file encryption, single file ACLs,
> etc...), they may go into the Capability attribute of the
> StorageEndpoint, which is an open enumeration, so we need to add
> nothing for that.
>
> Cheers,
>   Salvatore.
>
> On 05/11/2013 11:59, stephen.burke at stfc.ac.uk wrote:
>> glue-wg-bounces at ogf.org [mailto:glue-wg-bounces at ogf.org] On
>>> Behalf Of Salvatore Pinto said:
>>> That is true, Storage schema is very close to the Grid version and can
>>> be indeed rewritten inheriting the Storage elements or just modifyi-ing
>>> them. From my point of view, the big difference between Cloud and Grid
>>> storage is that Cloud storage is not file-oriented like the grid one
>>> but
>>> more object oriented (where an object can be a file, a disk image, a
>>> stream or a generic object). So, in this view, the "Grid" storage is a
>>> specialization of the "Cloud" one (where object type=files) and it
>>> would
>>> be probably better to change the GLUE 2.0 Storage element to consider
>>> objects instead of files and have one single entity. What do you think
>>> of that?
>> I don't think the  current schema really represents files - the word "file" may appear in the text but you could replace it with "data object" without changing anything. It isn't feasible to publish information about individual files, all we have is summary information about larger blocks of storage. Also storage systems presumably don't have the biggest difference between cloud and grid computing services, namely that they aren't persistent and can be created and destroyed - storage has to be persistent to be useful!
>>
>>> CDMI metadata are mostly related to file-level options, for example
>>> ACLs, file redundancy, file encryption, etc... (source:
>>> http://cdmi.sniacloud.com/cdmi_spec/16-metadata/16-metadata.htm). We
>>> could try to extend these attributes at system level and assign them to
>>> the storage service or other entities, but with this we would break one
>>> of the main features of the Cloud storage, which is the freedom for the
>>> user to ecrypt one file and not another, share one with the world, one
>>> with only his colleagues and another restricted.
>> You certainly wouldn't want to publish the state of individual files, but you may want to advertise the capability to do various things, similarly to the support for different access protocols.
>>
>> Stephen
>>
>
>
> -- 
> Salvatore Pinto
> Cloud Technologist, EGI.eu
> e-mail: salvatore.pinto at egi.eu
> skype: salvatore.pinto0
> Science Park 140, Amsterdam, The Netherlands
>
>
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> glue-wg mailing list
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> https://www.ogf.org/mailman/listinfo/glue-wg

-- 
==================================================
 Florido Paganelli
   ARC Middleware Developer - NorduGrid Collaboration
   System Administrator
 Lund University
 Department of Physics
 Division of Particle Physics
 BOX118
 221 00 Lund 
 Office Tel: 046-2220272 
 Email: florido.paganelli at REMOVE_THIShep.lu.se
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