Re: nfs4 write delegation status

From: "David V. Cloud" <david.v.cloud@gmail.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Andy Adamson <andros@netapp.com>,
	linux-nfs@vger.kernel.org, erveith@de.ibm.com,
	nfsv4@linux-nfs.org
Subject: Re: nfs4 write delegation status
Date: Fri, 24 Jul 2009 15:32:47 -0400	[thread overview]
Message-ID: <fe2cbb740907241232j49e672fbvb60512e35e5ac0ff@mail.gmail.com> (raw)
In-Reply-To: <20090724184429.GA16811@fieldses.org>

[-- Attachment #1.1: Type: text/plain, Size: 2220 bytes --]

A simple one could be found in the following paper,

http://www.usenix.org/events/fast07/tech/full_papers/gulati/gulati_html/nache.html

-David

On Fri, Jul 24, 2009 at 2:44 PM, J. Bruce Fields <bfields@fieldses.org>wrote:

> On Thu, Jul 23, 2009 at 02:11:46PM -0400, Andy Adamson wrote:
> >
> > On Jul 23, 2009, at 11:10 AM, Rick Macklem wrote:
> >
> >>>> I really don't want to enable write delegations until we figure
> >>>> out how
> >>>> to enforce them correctly against local (non-nfs) users of the
> >>>> exported
> >>>> filesystem as well.  In addition to breaking delegations on read
> >>>> opens,
> >>>> that means breaking delegations or doing a cb_getattr on
> >>>> operations like
> >>>> stat.
> >>>
> >>> do you know whether there are local FS where the maintainers at
> >>> least plan
> >>> to incorporate delegations?
> >>
> >> I'm not a Linux guy, so I'm not familiar with the internal structure,
> >> but...
> >> in general, I don't think the problem is with local file systems.
> >> Usually
> >> the problem is with local system call access. For example, if a
> >> process running locally on the server opens a file, the delegation
> >> should
> >> be recalled, so that changes done locally on the client get flushed
> >> back
> >> to the server. Also, a write delegation allows a client to do byte
> >> range
> >> locking locally in the client, so the write delegation needs to be
> >> recalled before anything gets a byte range lock locally in the server.
> >
> > The delegation implementation on the Linux server uses the vfs lease
> > subsystem, and so is integrated with local access - conflicting opens
> > done locally do recall delegations.  But the last time I looked, the
> > lease subsystem is not complete as it doesn't recall leases (nor
> > delegations) on remove, rename, etc. Another problem is that while write
> > delegations improve performance for certain workloads, they kill
> > performance for others.
>
> Are there any published results yet with real workloads?
>
> --b.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

[-- Attachment #1.2: Type: text/html, Size: 3335 bytes --]

[-- Attachment #2: Type: text/plain, Size: 138 bytes --]

_______________________________________________
NFSv4 mailing list
NFSv4@linux-nfs.org
http://linux-nfs.org/cgi-bin/mailman/listinfo/nfsv4