Re: svn commit: r1787216 - /subversion/site/publish/faq.html

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Re: svn commit: r1787216 - /subversion/site/publish/faq.html

Branko Čibej
On 16.03.2017 17:18, [hidden email] wrote:

> Author: julianfoad
> Date: Thu Mar 16 16:18:18 2017
> New Revision: 1787216
>
> URL: http://svn.apache.org/viewvc?rev=1787216&view=rev
> Log:
> Clarify the NFS FAQ a little.
>
> * faq.html
>   (nfs): Clarify by moving FSFS before BDB, adding emphasis to keywords,
>     and removing a historical link.
>
> Modified:
>     subversion/site/publish/faq.html
>
> Modified: subversion/site/publish/faq.html
> URL: http://svn.apache.org/viewvc/subversion/site/publish/faq.html?rev=1787216&r1=1787215&r2=1787216&view=diff
> ==============================================================================
> --- subversion/site/publish/faq.html (original)
> +++ subversion/site/publish/faq.html Thu Mar 16 16:18:18 2017
> @@ -1073,7 +1073,12 @@ server?
>      title="Link to this section">&para;</a>
>  </h3>
>  
> -<p>If you are using a repository with the Berkeley DB back end
> +<p>If you are using the <b>FSFS repository back end</b> (which has
> +been the default since Subversion 1.2), then storing the repository on
> +a modern NFS server (i.e., one that supports locking) should be
> +fine.</p>


Well in fact it is not fine and we've known that for a while. NFS does
not guarantee that file renames are atomic, which is a pretty
fundamental requirement for FSFS. Also file locking in NFS is not
exactly reliable, whether or not the server is "modern".

IMO we should change this whole section to one sentence: "Do not put
your repository on NFS or any other networked file system."

-- Brane
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Re: svn commit: r1787216 - /subversion/site/publish/faq.html

Daniel Shahaf-2
Branko Čibej wrote on Thu, Mar 16, 2017 at 18:10:02 +0100:
> Well in fact it is not fine and we've known that for a while. NFS does
> not guarantee that file renames are atomic, which is a pretty
> fundamental requirement for FSFS. Also file locking in NFS is not
> exactly reliable, whether or not the server is "modern".

> IMO we should change this whole section to one sentence: "Do not put
> your repository on NFS or any other networked file system."

I think that'd be too succinct.  How about:

    FSFS requires the syscalls rename(2) and flock(2) to work.  We are
    aware of no networked file system which satisfies this requirement.

Cheers,

Daniel
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Re: svn commit: r1787216 - /subversion/site/publish/faq.html

Mark Phippard-3
In reply to this post by Branko Čibej


On Thu, Mar 16, 2017 at 1:10 PM, Branko Čibej <[hidden email]> wrote:
On 16.03.2017 17:18, [hidden email] wrote:
> Author: julianfoad
> Date: Thu Mar 16 16:18:18 2017
> New Revision: 1787216
>
> URL: http://svn.apache.org/viewvc?rev=1787216&view=rev
> Log:
> Clarify the NFS FAQ a little.
>
> * faq.html
>   (nfs): Clarify by moving FSFS before BDB, adding emphasis to keywords,
>     and removing a historical link.
>
> Modified:
>     subversion/site/publish/faq.html
>
> Modified: subversion/site/publish/faq.html
> URL: http://svn.apache.org/viewvc/subversion/site/publish/faq.html?rev=1787216&r1=1787215&r2=1787216&view=diff
> ==============================================================================
> --- subversion/site/publish/faq.html (original)
> +++ subversion/site/publish/faq.html Thu Mar 16 16:18:18 2017
> @@ -1073,7 +1073,12 @@ server?
>      title="Link to this section">&para;</a>
>  </h3>
>
> -<p>If you are using a repository with the Berkeley DB back end
> +<p>If you are using the <b>FSFS repository back end</b> (which has
> +been the default since Subversion 1.2), then storing the repository on
> +a modern NFS server (i.e., one that supports locking) should be
> +fine.</p>


Well in fact it is not fine and we've known that for a while. NFS does
not guarantee that file renames are atomic, which is a pretty
fundamental requirement for FSFS. Also file locking in NFS is not
exactly reliable, whether or not the server is "modern".

IMO we should change this whole section to one sentence: "Do not put
your repository on NFS or any other networked file system."




This is news to me.  We have always stored all of our repositories on NFS.  I thought you just has to be on NFSv3 with file locking enabled?

Blair's tuning wiki seems to largely be about NFS as well:



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