Re: 10.2 NFS mount points

On Wednesday 01 February 2006 20:38, Mladen Gogala wrote:
> On 02/01/2006 09:35:25 PM, Chris Marquez wrote:
> > All this talk about Oracle & NFS. It has been a long time since I
> > looked, but hasn't Oracle always said "NO" to NFS (datafiles)? I'm not
> > talking about NAS like NetApp...I'm talking about setting up a home grown
> > NFS box and putting datafiles on it?...shoot I'm not even sure they
> > support many CFS's?
>
> Chris, the words of wisdom about datafiles and NFS were spoken a long
> time ago, ding the era of NFS v2. Since then, somewhere in 1994, SUN
> published specification for NFS v3. Differences were many, but among
> the two most important were locking and the ability to use TCP connection.
> Previously, in v2 protocol, NFS was using UDP and was stateless, just like
> http is today. When something is stateless, it is rather hard to lock it,
> so NFS v2 did not support locking. That would make it rather hard to
> operate a database. In addition to locking, NFS4 will add client side
> caching, which would speed things up enormously and async I/O and
> direct I/O will come standard.
> Some of it was previously available on Solaris (see cfsadmin) but not
> on most of the other unix versions as this features needed changes in
> the kernel as kernel is the part which performs I/O and decides about
> caching data blocks. So now with NFS4 you have async and direct I/O
> and client caching. Not much difference from a local disk at all.
> The old lore no longer applies. Really good summary can be found at:
>
> http://www.citi.umich.edu/projects/nfsv4
>
> Please, feel enlightened, by all means.

Mladen,

Your comment is absolutely true - the spec supports it. Your statement fails to recognize that even with NFS v3, there does not appear to be widespread USE of NFS over TCP/IP. From http://nfs.sourceforge.net/ we see

"
Client support for NFS over TCP is integrated into all 2.4 and later kernels.

Server support for TCP appears in 2.4.19 and later 2.4 kernels, and in 2.6 and later kernels. Not all 2.4-based distributions support NFS over TCP in the Linux NFS server.
"

Similar situations appear in various OSs. The choice of NFS over UDP seems based on a preference for performance over

Just an observation noting that the words of wisdom you mention may not have not been heeded to the extent we could wish.

/Hans

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