L. Dusseault
Internet Draft Xythos
Document: draft-dusseault-dav-quota-00.txt C. Warner
Expires: 2002 August 2001
Quota and Size Properties for DAV Collections
Status of this Memo
This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
WebDAV servers are frequently deployed with directory quota (size)
limitations. This Internet-Draft discusses the two properties and
minor behaviors needed to interoperably deal with quotas on WebDAV
repositories.
Table of Contents
Status of this Memo................................................1
Abstract...........................................................1
New Properties.....................................................2
DAV:quota ......................................................2
DAV:quotaused ..............................................2
Error reporting....................................................2
Notes..............................................................2
References.........................................................4
Author's Addresses.................................................4
Dusseault Informational - Expires February 2002 1
DAV Collection Size and Quota August 2001
New Properties
DAV:quota
The DAV:quota property is used to express, in bytes, the total
amount of storage space allocated to a directory. The value of this
property will usually be protected, although a user with sufficient
privileges may be permitted to change the value.
DAV:quotaused
The DAV:quotaused value is calculated by the server to indicate
approximately how much storage space is already taken up in this
directory (in bytes). It includes sub-directories and all resources
inside those subdirectories. It is optional. The value need not be
entirely accurate but must be at least as accurate as the client
could calculate themselves by summing values for ôgetcontentlengthö.
If the value cannot be made more accurate, then this property should
be omitted. Support for this property enhances the client
experience, because together with DAV:quota, the client can manage
its files to avoid running out of allocated storage space. Clients
may not be able to calculate the value adequately on their own,
depending on how storage, including resource bodies and perhaps
property values, is counted by the server.
Error reporting
WebDAV (RFC2518) defines the status code 507 (Insufficient Storage).
This status code should be used when a client request (e.g. a PUT,
PROPFIND, MKCOL, MOVE or COPY) is forbidden because it would exceed
their allotted quota. In order to differentiate the response from
other storage problems, the server should include an XML error body
with the precondition tag, as defined
by DeltaV.
HTTP/1.1 507 Insufficient Storage
Content-Length: 100
Content-Type: text/xml
Notes
Server implementations store and account for their data in many
different ways. Some of the challenges:
- Some server implementations find it prohibitive to count property
value size, others may choose to close that loophole for better
accounting.
- Older versions of resources may be stored as well.
Dusseault Informational - Expires February 2002 2
DAV Collection Size and Quota August 2001
- Variants of one resource may exist with different content lengths
- Content may be dynamically generated.
- Resource bodies can be compressed
Since server storage accounting can vary so much, clients should
expect the following :
- The size of a file on the clientÆs file system, or in a PUT
message, may not correspond to the amount of storage required by the
server to store the resource. Thus, the client cannot predict 100%
accurately whether a given file will be allowed given the storage
quota.
- Deleting a resource may not free up the same amount of storage as
indicated by the ôgetcontentlengthö value for the resource. If
deleting a resource does not free up any quota, the file has
probably been moved to a ôtrashö folder or ôrecycle binö.
- The size or ôquotausedö is not necessarily a sum of the
ôgetcontentlengthö properties for resources stored in the directory.
Dusseault Informational - Expires February 2002 3
DAV Collection Size and Quota August 2001
References
Author's Addresses
Lisa Dusseault
Xythos
77 Maiden Lane, Suite 200 Phone: 1-415-248-9004
San Francisco, CA, USA Email: lisa@xythos.com
Clark Warner
Email: clark@thewarners.com
Dusseault Informational - Expires February 2002 4