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Re: Review of draft-ietf-webdav-quota-02.txt

From: Brian Korver <briank@xythos.com>
Date: Thu, 11 Dec 2003 10:53:11 -0800
Message-Id: <44E15905-2C0B-11D8-8BCD-000A95AACED2@xythos.com>
Cc: WebDAV <w3c-dist-auth@w3.org>
To: Chris Sharp <csharp@apple.com>

On Dec 11, 2003, at 10:30 AM, Chris Sharp wrote:
> Just getting around to understanding this thread. I totally agree, the 
> quota-assigned-bytes seems unnecessary and confusing.

It does seem to be confusing to people.  Do you have a proposal for an
alternative mechanism (or at least wording) that accomplishes
the same thing?  Specifically, a mechanism set the quota (especially in
face of quota systems like the one you give in the example where
quota constraints are inherited from the parent)?



>
> On another note, I think there needs to be some clarification the way 
> quota-available-bytes and quota-used-bytes work.
>
> Example:
>
> Initial State of Repository with a Quota management system:
>
>                                                                  
> DAV:quota-available-bytes   DAV:quota-used-bytes
>         /A                                                     95MB    
>                                      5MG <--- used for somewhere for 
> something
>         /A/UploadDirectory                      10MB                   
>                        0
>
> A new 5MB resource is created at  /A/UploadDirectory/new5MBFile:
>                                                                  
> DAV:quota-available-bytes   DAV:quota-used-bytes
>         /A                                                     90MB    
>                                      10MB
>         /A/UploadDirectory                      5MB                    
>                         5MB
>
> Pretty clear, however, if there is no quota differentiation on 
> /A/UploadDirectory, the current draft of the RFC makes 
> quota-used-bytes, which is really inherited from its parent, 
> incongruent with quota-available-bytes on the same resource.

That's just one example of a quota system.  As the draft points out:

    Note that this is only one example quota system, and that other
    quota systems are possible.

Do you think the text would benefit from having an example given using
a different quota system?  I'm starting to think that would be a good
idea.

The draft does not mandate any particular quota system.  IMHO it would
be a bad idea to do so.





>  A diagram is in order:
>
> Initial State of Repository with a Quota management system:
> (quota system on /A only)
>                                                                  
> DAV:quota-available-bytes   DAV:quota-used-bytes
>         /A                                                     95MB    
>                                      5MG
>
> A new 5MB resource is created at  /A/UploadDirectory/new5MBFile:
>                                                                  
> DAV:quota-available-bytes   DAV:quota-used-bytes
>         /A                                                     90MB    
>                                      10MB
>        /A/UploadDirectory                       90MB                   
>                       5MB
>
> The sum of quota-available-bytes and quota-used-bytes is 95 on  
> /A/UploadDirectory and not 100! Logically, if you get a request for 
> quota-available-bytes on a resource /A/UploadDirectory and the quota 
> is actually enforced on the parent, that you would essentially walk up 
> the tree until you found an appropriate "mount point" based quota 
> requirement. If this is true, the quota-used-bytes should do the same 
> thing. Meaning, quota-used-bytes on  /A/UploadDirectory would be the 
> same as quota-used-bytes /A if /A/UploadDirectory did not contain a 
> more specific quota rule.
>
> This is also an efficiency win for implementors. If an implementation 
> has to support quota-used-bytes on an arbitrary URL, it is impractical 
> to think that quota-used-bytes could be incrementally adjusted and 
> would necessarily need to be calculated on-the-fly, which does not 
> scale well for most implementations.
>
> How NFSv4 handles this situation?
>
>
> Also, under the "Notes" section, "What clients should expect" seems to 
> have a sentence which is not grammatically correct.
> "This allows the space used by /~milele/public/ to be as
>     large as the quota on /~milele/ allows (depending on the other
>     contents of /~milele/) even if the quota on /~milele/ is changed."
>
> Regards,
>
> Chris.
> On Nov 14, 2003, at 2:27 AM, Stefan Eissing wrote:
>

-brian
briank@xythos.com
Received on Thursday, 11 December 2003 13:53:17 GMT

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