[glue-wg] Suggestion for splitting the StorageShare.

[Sergio Andreozzi]

Hi Laurence,


Laurence Field wrote:
> On further investigation of the Storage Schema an unmet use case has 
> been found.
> 
> Use Case: Consider two VOs who use two different paths to access the 
> same StorageShare or alternatively one VO who can access the same 
> StorageShare via two different paths. Where there could be an asymmetry 
> with the ACLs for the SRM v2.2 space and the Path.
> 
> The latest schema would require a StorageShare to be instantiated for 
> each combination of path and SRM v2.2 space ACL, leading to n*m storage 
> shares duplicating a great deal of information.

it is better to state that the use cases are supported, but at the price 
or redundancy of information in certain situations.

This was discussed several times and a final choice was made around a 
month ago. We opted to go for simplicity at the cost of redundancy.

The criterion for choosing among the different approaches was to 
privilege simplicity in querying the information even though redundant 
data may need to be published in some situation.

There is no real best solution. As Maarten described, you may have 
either big VO's with their own dedicated shares (so no redundancy) and 
small VO's sharing the same storage shares (redundancy occurs).

For a while, we had a more "normalized" schema. The price to pay is a 
complexity of relationships and an higher cost at selection time (thing 
about making all the combinations in order to find out the best 
solution). And also keep in mind that representing associations does 
have a fixed cost of two attributes.

If you really want to discuss again this, you should first draw a 
complete picture with all the entities, relationships and multiplicity 
(e.g., what about Capacity-like entities?). Otherwise, it may look 
simpler but it isn't when you go deeper into the details.


Cheers, Sergio

> 
> The suggested solution is to split the StorageShare into the 
> StorageShare and StorageEnvironment where there is a one to many 
> relationship between the Environment and the Share. Both entities 
> inherit the ACLs from the AccessPolicy
> 
> StorageShare
> LocalID
> Path
> Tag
> 
> StorageEnvironment
> LocalID  
> ServingState
> AccessLatency
> RetentionPolicy
> ExpirationMode
> DefaultLifeTime
> MaximumLifeTime
> 
> At the same time this allows the AggregationID to be removed.
> 
> 
> 
> 
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-- 
Sergio Andreozzi
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