[mythtv-users] Fine-tuning NFS parameters

[Gavin Hurlbut]

On Fri, Jul 23, 2010 at 4:56 PM, Kevin Ross <kevin at familyross.net> wrote:

> On 07/23/2010 04:21 PM, Gavin Hurlbut wrote:
>
>> But for a minimum, on the client side, mount with options:
>> soft,posix,bg,intr,rsize=32768,wsize=32768,nfsvers=3
>>
>>
> I looked up your mount options.  It seems some are not necessary, and at
> least one is deprecated.
>
> soft: not performance related, personal preference on hard vs. soft.
>
> posix: couldn't find a reference in my man page
>
> bg: not performance related, personal preference on fg vs. bg.
>
> intr: deprecated
>

Not deprecated in my man page.



> rsize/wsize: The "TRANSPORT METHODS" section of the man page says you
> should specify rsize and wsize when using UDP, not when using TCP.  And all
> modern NFS implementations use TCP.
>


> nfsvers: autonegotiated to 3 if both sides support it, otherwise 2.  So
> this seems unnecessary also.
>

If your NFS server doesn't require the options, great.  However...  If it
does NOT, you should do it...

nfsvers=3 is a minimum.  If both sides do not support 3, you want the mount
to FAIL.  NFSv2 does not support files > 2GB in size, making it absolutely
useless for mythtv recordings.

As for the rsize/wsize...  I don't care what your man page indicates, those
are the parameters to tweak for performance in NFS.  If your setup defaults
to good settings, great.  I would not presume that "all modern...." means
squat.  I have seen "modern" NFS implementations that use UDP, and that
require the options stated.

The *default* rsize/wsize for many NFS servers is 4k.  This sucks really
badly for performance, especially on GigE.


> Gavin, I don't mean to be picking on you.  I just wanted to see if those
> options were better than sticking with defaults. So I looked up the options
> you recommended, but it seems those might not be ideal, either.
>

OMG.  If you want "ideal", then you'd better start running bonnie and get
tweaking for your system.


> Also, the "async" option I recommended appears to only apply when writing
> to an NFS mount, not reading from it.  Since the OP will presumably only be
> reading from NFS, async mode probably won't buy him anything.  So sticking
> with the defaults will probably be perfectly fine.


Possibly.  Another useful one:  proto=tcp (or proto=udp) (or simply tcp or
udp).

Anyways, go ahead and play to your own satisfaction :)
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