Subject: Re: [HACKERS] PostgreSQL, NetBSD and NFS
To: None <,>
From: Luke Mewburn <>
List: current-users
Date: 02/02/2003 00:41:24
On Fri, Jan 31, 2003 at 11:15:17AM -0700, Rick Kelly wrote:
  | Back in the mid-nineties, when I worked for Progress Software, their
  | software would refuse to open a database that was mounted with NFS.
  | The main reason was that Progress felt that they couldn't guarantee 
  | the integrity of the data. As far as I know, Oracle, Informix, and
  | Sybase had similar restrictions at that time.
  | Has NFS changed so drastically that it no longer has data integrity
  | problems?
  | I've used NetApp filers for lots of different jobs, but never for 
  | databases.

Chances are the problem you're seeing here is in the NetBSD NFS
client code, or the PostgreSQL code, not the NetApp filer.

Certain database vendors (including Oracle) have certified certain
NFS vendors (including NetApp filers, and I believe EMC Celerra)
for use as back end file store for their databases when run on
certain NFS clients (such as Solaris/sparc).

(If I recall correctly, Oracle use NetApps behind their in-house
databases.  They certainly support it, and many large clients are
using it that way.  Check out

There's a lot of FUD about running databases over NFS (or even on a
file system versus raw disk).  This FUD might have had a valid point
years ago, but NFS file servers have progressed a long way in the
last few years.  They can also provide functionality which is
extremely useful.  For example, using systems like NetApp filers
allows you to use the "snapshot" mechanism in such devices to do
stuff like:

	client:	put database in hot backup mode

	filer:	create snapshot (takes a few seconds)

	client:	take database out of hot backup mode (only been there
		for a few seconds, not the hours it often takes with
		"traditional" hot backups)

	filer:	backup snapshot, and/or "snapmirror" it to a remote
		filer for almost instant recovery

(This does not require the `3N' disk that a "3 way mirror with one
mirror slice broken off as the hot backup" that certain other vendors
use to solve this problem.)