Re: Update section on NFS

On 4/23/19 6:10 AM, Peter Eisentraut wrote:
> Attached is a patch that rewrites the section on NFS. The old section
> was ancient and didn't seem very helpful.
>
> AFAIK, the only strict requirement for using NFS with PostgreSQL is the
> hard mount. Anything else we should mention?
>
> I also reorganized the sectioning so that information about other file
> systems can be added more easily.

> <para>
> - Many installations create their database clusters on network file
> - systems. Sometimes this is done via <acronym>NFS</acronym>, or by using a
> - Network Attached Storage (<acronym>NAS</acronym>) device that uses
> - <acronym>NFS</acronym> internally. <productname>PostgreSQL</productname> does nothing
> - special for <acronym>NFS</acronym> file systems, meaning it assumes
> - <acronym>NFS</acronym> behaves exactly like locally-connected drives.
> - If the client or server <acronym>NFS</acronym> implementation does not
> - provide standard file system semantics, this can
> - cause reliability problems (see <ulink
> - url="https://www.time-travellers.org/shane/papers/NFS_considered_harmful.html"></ulink>).
> - Specifically, delayed (asynchronous) writes to the <acronym>NFS</acronym>
> - server can cause data corruption problems. If possible, mount the
> - <acronym>NFS</acronym> file system synchronously (without caching) to avoid
> - this hazard. Also, soft-mounting the <acronym>NFS</acronym> file system is
> - not recommended.

<snip>

> + <para>
> + It is possible to use an NFS file system for storing the
> + <productname>PostgreSQL</productname> data directory. The only
> + requirement is that the file system is mounted using the
> + <literal>hard</literal> option. With the <literal>hard</literal> option,
> + processes can <quote>hang</quote> indefinitely if there are network
> + problems, so this setup will require a careful monitoring setup. (The
> + <literal>soft</literal> option will interrupt system calls in case of
> + network problems, but the <productname>PostgreSQL</productname> will not
> + repeat system calls interrupted in this way, so any such interruption
> + will result in an I/O error being reported.)
> + <productname>PostgreSQL</productname> does nothing special for
> + <acronym>NFS</acronym> file systems, meaning it assumes
> + <acronym>NFS</acronym> behaves exactly like locally-connected drives.
> + </para>

Looks like you dropped the advice WRT the asynchronous mount option.
Isn't that is still relevant?

Joe

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