Subject: [nfsv4] [FedFS] Multiple FSL resolution

From: <[email-masked]>
Date: Wed, 9 Dec 2009 21:36:46 -0500

Either an easily answered question or a possible topic for discussion in
tomorrow's FedFS call.

The requirements spec
(http://www.ietf.org/id/draft-ietf-nfsv4-federated-fs-reqts-06.txt)
talks about associating multiple FSL's with an FSN where the file sets
referred to by the FSL's are replicas of one another.  Maintenance of
the replicas is outside the scope of FedFS.    

When a client traverses a junction that refers to an FSN which has
multiple FSL's associated with it the file server queries the relevant
NSDB for the FSLs associated with the FSN (section 3.2, step 4).    But
only one of the potentially multiple FSLs is returned to the client in
the form of a protocol specific referral (section 3.2, step 5).      

How does the server decide which of multiple FSLs to return to a client?

Thanks,

Chris

-- 
Chris Stacey - Senior Technologist, Celerra Unified Storage Engineering,
EMC Corporation (New Zealand).  Phone: +64 21 225 3747

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From: "Everhart, Craig" <[email-masked]>
Date: Thu, 10 Dec 2009 11:05:23 -0500

As a quick shot, I believe that section 3.2, step 5, is in error, at
least for the case of NFSv4{,.1}, which is the domain of discourse here.
All the FSL's for a given FSN should be converted and sent to the file
server client, and the client can choose among them.

There are possible opportunities for introduction of policy-controlled
behavior if there are more FSL's than a given server can convert or than
it can communicate to the file server client, but the idea is that the
file servers take all locations from the NSDB and present them all to
the client for its choice.

                                Craig

From: [email-masked] [mailto:[email-masked]] 
Sent: Wednesday, December 09, 2009 9:37 PM
To: [email-masked]
Subject: [nfsv4] [FedFS] Multiple FSL resolution

The requirements spec

Thanks,

Chris

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From: James Lentini <[email-masked]>
Date: Thu, 10 Dec 2009 11:18:38 -0500 (EST)

On Wed, 9 Dec 2009, [email-masked] wrote:

> tomorrow’s FedFS call.

We can certainly discuss this during today's meeting. I will place it 
on the agenda.

> 
> The requirements spec
> (http://www.ietf.org/id/draft-ietf-nfsv4-federated-fs-reqts-06.txt) talks
> about associating multiple FSL's with an FSN where the file sets referred to
> by the FSL's are replicas of one another.  Maintenance of the replicas is
> outside the scope of FedFS.   
> 
>  
> 
> When a client traverses a junction that refers to an FSN which has multiple
> FSL's associated with it the file server queries the relevant NSDB for the
> FSLs associated with the FSN (section 3.2, step 4).    But only one of the
> potentially multiple FSLs is returned to the client in the form of a
> protocol specific referral (section 3.2, step 5).     

This text is only an example. If client access protocol supports 
multiple referral targets, the fileserver may return more than one. In 
fact, NFSv4's fs_locations and NFSv4.1's fs_locations_info allow for 
multiple targets.

> How does the server decide which of multiple FSLs to return to a 

The process the server uses is implementation specific. The server 
might return all the FSLs or have some algorithm for picking a subset 
of the FSLs.

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From: Nicolas Williams <[email-masked]>
Date: Mon, 14 Dec 2009 10:43:37 -0600

> the client for its choice.

Indeed, you might not want the server to take too long resolving a
junction.  So if there's 10 FSLs the server might return as many as it
can resolve in, say, 10 seconds.

An implementation guideline should be included encouraging server
implementors to make junction resolution as parallel as possible.

Nico
--

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From: "Everhart, Craig" <[email-masked]>
Date: Mon, 14 Dec 2009 12:49:08 -0500

Nico, what do you mean "resolving" a junction?  I'd expect that the
server consults the listed NSDB, looks up the entry for the FSN, gets
the list of FSLs, and passes some/most/all of them to the FS client.
The file server shouldn't have to further resolve the FSLs, nor should
it have to consult more than one NSDB for the list of FSLs.  Would this
be incorrect?

Or are you speaking of resolving multiple junctions for multiple queries
from FS clients?

		Craig

-----Original Message-----
From: Nicolas Williams [mailto:[email-masked]] 
Sent: Monday, December 14, 2009 11:44 AM
To: Everhart, Craig
Cc: [email-masked]; [email-masked]
Subject: Re: [nfsv4] [FedFS] Multiple FSL resolution

Nico
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nfsv4 mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/nfsv4

---

From: Nicolas Williams <[email-masked]>
Date: Mon, 14 Dec 2009 12:14:12 -0600

> the list of FSLs, and passes some/most/all of them to the FS client.

I mean exactly that: the process of obtaining a list of nfs4_locations
to return to the client.

> it have to consult more than one NSDB for the list of FSLs.  Would this

Right.

Nico
--