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References: <1382807547.29041.12.camel@heisenberg.scientia.net> <20131027191512.GA31322@fieldses.org> <1382911068.6932.20.camel@heisenberg.scientia.net> <8DB0D7A2-BA2A-4001-A01C-D498C777B243@netapp.com> <1382920068.6932.46.camel@heisenberg.scientia.net> <2E672741-FE4F-4287-8D00-B7634A71709E@netapp.com> <526E8562.3040809@redhat.com> <1382976943.8774.10.camel@heisenberg.scientia.net> <FD29488A-348B-48BA-9B1D-4ACF997BC794@netapp.com> <526EA65A.7010209@redhat.com> <20131028180838.GG31322@fieldses.org> <526EAD86.6090507@redhat.com>
To: spencer.shepler@gmail.com
Cc: Dr Fields James Bruce <bfields@fieldses.org>,
        Christoph Anton Mitterer <calestyo@scientia.net>,
        Mailing List Linux NFS <linux-nfs@vger.kernel.org>,
        linux-nfs-owner@vger.kernel.org, Steve Dickson <SteveD@redhat.com>,
        "Myklebust, Trond" <Trond.Myklebust@netapp.com>,
        "Ric Wheeler" <ric.wheeler@usenix.org>, nfsv4@ietf.org
MIME-Version: 1.0
Subject: Re: XATTRs in NFS?
From: Marc Eshel <eshel@us.ibm.com>
Message-ID: <OFA4C7B613.86F16AC7-ON88257C12.006FE486-88257C12.0071EE79@us.ibm.com>
Date: Mon, 28 Oct 2013 13:44:25 -0700
Content-Type: text/plain; charset="US-ASCII"
Sender: linux-nfs-owner@vger.kernel.org
List-ID: <linux-nfs.vger.kernel.org>

Hi Spencer, 
Is it still possible to get on the agenda fir IETF 88, I just got approval 
to travel. We can use about 15 minutes, or what ever is available to 
discussion the future of named attributes in NFS. The two main questions 
that we need answer are: 
1. Do we need them? what applications use them and how. 
2. Can we have a more simple model that handles just user attributes.

Input is welcome to help me make the case at the meeting.

Thanks, Marc.




From:   Ric Wheeler <rwheeler@redhat.com>
To:     Dr Fields James Bruce <bfields@fieldses.org>, 
Cc:     "Myklebust, Trond" <Trond.Myklebust@netapp.com>, Christoph Anton 
Mitterer <calestyo@scientia.net>, Mailing List Linux NFS 
<linux-nfs@vger.kernel.org>, Steve Dickson <SteveD@redhat.com>
Date:   10/28/2013 11:32 AM
Subject:        Re: XATTRs in NFS?
Sent by:        linux-nfs-owner@vger.kernel.org



On 10/28/2013 02:08 PM, Dr Fields James Bruce wrote:
> On Mon, Oct 28, 2013 at 02:00:58PM -0400, Ric Wheeler wrote:
>> On 10/28/2013 01:49 PM, Myklebust, Trond wrote:
>>> On Oct 28, 2013, at 12:15 PM, Christoph Anton Mitterer 
<calestyo@scientia.net> wrote:
>>>
>>>> On Mon, 2013-10-28 at 11:40 -0400, Ric Wheeler wrote:
>>>>> Then you end up with large directories and an extra name per inode 
that needs to
>>>>> be stored and extra lookups for each file when you do a whole file 
system crawl.
>>>>>
>>>>> Certainly not as easy as adding and xattrs with that information :)
>>>> And I think there's another reason why it wouldn't work...
>>>>
>>>> Imagine I change my system to encode what should be XATTRs in 
hardlink
>>>> pseudo files...
>>>>
>>>> If I have such pair locally e.g. on my ext4:
>>>> /foo/bar/actual/file
>>>> /meta/<SHA512 identifier>.2342348324
>>>>
>>>> And now move/copy the file via the network to the archive, I'd have 
to
>>>> copy both files (which is really annoying), and I'd guess the inode
>>>> coupling would get los (and at least the name wouldn't fit anymore).
>>>>
>>>> So the whole thing is IMHO not even a workaround.
>>> OK. So you're going to do XATTRs for us?
>>>
>>> Trond
>> Now that pNFS is perfect and labeled NFS has made it upstream, I
>> think that Steve D must be looking for something to keep him busy :)
> I agree with Trond that we first really need good evidence about exactly
> who wants this and why.
>
> --b.

For the user space xattrs, many applications store various types of 
metadata. 
Gluster for example heavily uses xattrs, other programs do things like 
data 
scrubbing (look for a long unchanged file, compute a has and store it as 
an 
xattr) or simply use it to annotate the file with the name of the program 
that 
created it. Think of it as file decorations or annotations.

Today, if we store files in NFS that have xattrs, we do in fact cause data 
loss.

I can understand an answer of "this would be hard to do for NFS and need 
to go 
through IETF" but think that xattrs are well enough established in Linux 
and 
supported in the tool chain that it is way too late to question whether or 
not 
supporting them is a worth our time.

Ric

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