Quick performance question

[gaf-mNDKBlG2WHs at public.gmane.org (Jerry Feldman)]

On 08/06/2010 03:31 PM, Bill Bogstad wrote:
> On Fri, Aug 6, 2010 at 2:01 PM, Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org> wrote:
>  =20
>> Currently I am using a RHEL 5.2 server to export a number of files via=

>> NFS. Simple. On the other servers, I use autofs to mount the
>> directories. In preparation for moving the directories (about 800GB) t=
o
>> a dedicated NFS server, what I plan to do is:
>> (1) rename the /mnts directory to /exports. This should have been done=

>> when I set up the server a few years ago. (The reason for the /mnts na=
me
>> is that I need to mirror Toronto.
>>
>> (2) then I want to mount the directories in /exports onto
>> localalhost:/mnts. But, I want to use the same auto.mnts file on the n=
fs
>> server that I do on the other 7 systems. So I can use the line:
>> *          -fstype=3Dnfs,rw,nosuid,soft      <nfs server name>:/export=
s/&
>>
>> I certainly can use
>> *          -fstype=3Dnfs,rw,nosuid,soft      localhost:/exports/&
>>
>> Is the Linux kernel smart enough to recognize that <nfs server name> i=
s
>> really the local host, and not send the bits out to the interface. I'm=

>> almost certain that the bits never go out on the network, but I just
>> want to confirm it.
>>    =20
> If <nfs server name> resolves to an IP address associated with some
> real or virtual interface on the local machine, no packets will be
> sent out on any physical interface.  (You might be able to set up some
> very weird routing tables, to change this; but it won't happen with
> any standard network configuration.)  This is true whether we are
> talking about NFS, telnet, or any other network protocol.
>
> OTOH, I think you might want to rethink doing it this way.  You'll
> probably get better local IO performance on the server, if you don't
> do force all local IO to those filesystems through NFS.   I haven't
> kept up with benchmarks, but in the past Linux hasn't had good NFS
> server performance.   I'm not sure what the best way to do this would
> be, but you might look into manually setting up symbolic links or
> possibly using the --bind option to the mount command.
>
>  =20
Thanks Bill,
I was pretty confident that Linux did keep packets locally.
Currently the system is in transition. It serves about 900GB data, but I
am moving this to another device, and the objective is to use the same
automount scripts on this machine as my other 8. Certainly symlinks will
work. But, since I will be mounting from an external device in the
future, using the bind option solves another issue. Once the migration
is complete, this becomes a non-issue.

--=20
Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org>
Boston Linux and Unix
PGP key id: 537C5846
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