[Gluster-users] UDP instead of TCP?

Paul Robert Marino prmarino1 at gmail.com
Mon Sep 23 21:26:06 UTC 2013

Well thats true too, but what I was getting at was a little different.
The last valid reason I heard to use NFS over UDP was in the late
2000's. The argument was that it was being used over believe it or not
an ISDN leased line because the remote site in question was located in
a country where the internet service wasn't reliable enough to make an
IPSEC tunnel over the internet a viable option. In that case it was
still practical to use UDP for transport because due to the slow link
speed and high latency UDP transport was significantly faster. further
more since the modems themselves handled guaranteed delivery of data
at layer 2 regardless of the layer 3 protocol so it made a lot of

That said this is starting to go on a tangent.

Essentially TCP is the way to go nowadays with NFS except in very rare
cases, and just about every client written in the last decade supports
it including ESXi and vCenter.

here is a quote from
VMware vSphere implementation of NFS supports NFS version 3 in TCP.
There is currently no support for NFS
version 2, UDP, or CIFS/SMB.

On Mon, Sep 23, 2013 at 3:41 PM, Jeff Darcy <jdarcy at redhat.com> wrote:
> On 09/23/2013 03:31 PM, Paul Robert Marino wrote:
>> In general link speeds are fast enough that TCP is preferred for NFS. The
>> UDP
>> transport is a vestige of running NFS over network connections that were
>> slower
>> than the disk they would read and write from nowadays the reverse is
>> generally
>> true and TCP is the safer transport method.
> To be a bit more specific, on modern networks NFS over UDP is susceptible to
> fragment-ID wraparound which could lead to data corruption.  This has been
> well known since at least 2006[1].  On modern machines the difference in
> processing time between TCP and UDP is negligible, so there's just no good
> reason to take that risk.  BTW, I've been using/developing NFS since v2 in
> 1990, when the difference really might have mattered.  If I can see that NFS
> over UDP is past its sell-by date, so can anybody else.  ;)
> [1] http://nfsworld.blogspot.com/2006_03_01_archive.html

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