Subject: [nfsv4] New pNFS ID available

From: Garth Goodson <[email-masked]>
Date: Mon, 18 Jul 2005 12:53:50 -0700

I have made a number of updates to the pNFS draft based on feedback from 
the last informal gathering (open issues and comments have been 
commented as such within the draft).  The new draft has now been posted 
on the IETF's site.

http://www.ietf.org/internet-drafts/draft-welch-pnfs-ops-03.txt

-Garth

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From: Marc Eshel <[email-masked]>
Date: Thu, 21 Jul 2005 16:52:28 -0700

> http://www.ietf.org/internet-drafts/draft-welch-pnfs-ops-03.txt

I have few questions, comments regarding the new draft.

The high level requirement that I have to be able to support cluster file 
system is that a metadata server can also act as a data server. From 
reading this document I don't see a problem doing it but if someone think 
otherwise please let me know why. 

>       2.3  Storage Device
>               ...
>          A storage device could be another NFS server, or an Object 
Storage
>From reading this document it sound like the data server will have to be 
at the minimum NFSv4. There was some talk in the beginning about using 
NFSv3 as a data server but it is not being considered anymore right?

>       [OPEN ISSUE: should aggregation schemes (striping) be moved up a
>       level and made not opaque.  I.e., there would exist a generic
I think yes since we can use them to provide hints on the Open which is 
common to all storage devices. 

>       3.3  Obtaining a Layout
>       ...
>       The API used by the client to talk to its drivers is
>       outside the scope of the pNFS extension.  The storage protocol
>       between the client's layout driver and the actual storage is 
covered
>       by other protocols specifications such as SBC (block storage), OSD
>       (object storage) or NFS (file storage).

Is there a draft for file storage protocol? where can I find it?

Thanks, Marc.

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From: Garth Goodson <[email-masked]>
Date: Thu, 21 Jul 2005 17:01:20 -0700

> otherwise please let me know why. 

The issues outlined in Dave Noveck's previous comments still remain.  As 
far as the spec is concerned there is a single metadata server and only 
I/O ops are to be issued to data servers (the wording still exists).

> NFSv3 as a data server but it is not being considered anymore right?
This specification talks only about NFSv4 as the data server (and not we 
are not advocating that an unmodified NFSv4 server can be a data 
server).  An additional specification would have to be made if V3 were 
to be a storage protocol (like for objects and blocks).

> common to all storage devices.

Even if the striping is hidden (opaque), it can be used to provide an 
hint to whatever layer is doing data allocation as long as that layer 
understands the opaque layout (which I think it would have to).

> Is there a draft for file storage protocol? where can I find it?
It is included in the doc.  Section 5, page 26.

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From: Marc Eshel <[email-masked]>
Date: Thu, 21 Jul 2005 17:28:29 -0700

> I/O ops are to be issued to data servers (the wording still exists).

I know a single metadata server but I did not see anything that will 
preclude it from also acting as a data server.

> It is included in the doc.  Section 5, page 26.

That is what I thought but I wanted to make sure. So I don't see how the 
NFS client interface with the different layout drivers and for the file 
layout driver how it establishes communications with the NFS data server. 
Few things need to happen before you can send a read/write request to the 
NFS data server. In other words I should be able to implement the NFS file 
base protocol using only this document but I am sure I can.
Marc.

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From: Garth Goodson <[email-masked]>
Date: Thu, 21 Jul 2005 18:11:53 -0700

Marc Eshel wrote:
>>>The high level requirement that I have to be able to support cluster 
> 
> file 
> 
>>>reading this document I don't see a problem doing it but if someone 
> 
> think 
> 
You are correct.  It is a requirement that data can also be sent to the 
metadata server through normal V4 commands.  Additionally, there isn't 
anything precluding the metadata server from naming itself in a layout 
to be used as a data server.

> base protocol using only this document but I am sure I can.

We don't define how the NFS client interfaces with layout drivers, that 
is client side implementation specific and can be done in many ways 
(although arguably useful for interoperability), but I don't believe it 
is required to build a working file's-based client.

-Garth

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From: Marc Eshel <[email-masked]>
Date: Fri, 22 Jul 2005 17:20:25 -0700

>   If data are reorganized from a storage
>   device with a given device ID to a different storage device (i.e., if
>   the mapping between storage device and data changes), the layout
>   describing the data MUST be recalled rather than assigning the new
>   storage device to the old device ID.

If the device ID changes we can recall all layout that include the changed 
id but we also need to update the device list that the client cached. How 
do we do it? can we add a call to invalidate the device list on the 
client?
Marc.