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Re: Quota: another DAV:quota-assigned-bytes question

From: Julian Reschke <julian.reschke@gmx.de>
Date: Wed, 08 Sep 2004 08:04:15 +0200
Message-ID: <413EA0DF.5020709@gmx.de>
To: Brian Korver <briank@xythos.com>
CC: WebDAV <w3c-dist-auth@w3.org>

Brian Korver wrote:

> I was responding to an earlier suggestion that
> the model be scrapped in favor of one you proposed
> not doing.  We agreed to the quota-by-resource model,
> no one has proposed doing any other, so the issue
> is resolved.

I can't remember that anybody agreed on that (pointer, please?). The 
only p.o.v. that makes sense to me is that the Quota protocol only 
discusses marshalling, but not the Quota system itself. Thus it should 
work both with user/group-based and resource-based quota (and other 
systems that may exist).

> But, to answer your questions: Yes, the NFS spec does
> seem to allow disk limits to me marshalled through
> the quota properties and certainly doesn't prohibit
> this ("the server is at liberty to choose").  NFS
> chooses to define these properties as read-only.

RFC3530, section 5.10:

          Note that there may be a number of distinct but overlapping
          sets of files or directories for which a quota_used value is
          maintained (e.g., "all files with a given owner", "all files
          with a given group owner", etc.).

          The server is at liberty to choose any of those sets but should
          do so in a repeatable way.  The rule may be configured per-
          filesystem or may be "choose the set with the smallest quota".

So no, this doesn't apply to disk limits - disk limits are *not* quotas. 
RFC3530 discusses disk limits in section 5.6:


    space_free          43   uint64         READ     Free disk space in
                                                     bytes on the
                                                     filesystem
                                                     containing this
                                                     object - this should
                                                     be the smallest
                                                     relevant limit.

    space_total         44   uint64         READ     Total disk space in
                                                     bytes on the
                                                     filesystem
                                                     containing this
                                                     object.

    space_used          45   uint64         READ     Number of filesystem
                                                     bytes allocated to
                                                     this object.

Also note that RFC3530 distinguishes error conditions for both (section 12):

    NFS4ERR_DQUOT         Resource (quota) hard limit exceeded. The
                          user's resource limit on the server has been
                          exceeded.

and

    NFS4ERR_NOSPC         No space left on device. The operation would
                          have caused the server's filesystem to exceed
                          its limit.


So again, lett's just do what NFS does: define properties for quota and 
disk limits, keep the quota definitions such as they are compatible with 
existing quota systems, distinguish error conditions clearly and keep 
things read-only.

Best regards, Julian


-- 
<green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760
Received on Wednesday, 8 September 2004 06:04:59 GMT

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