[mythtv-users] Fine-tuning NFS parameters

belcampo belcampo at zonnet.nl
Sat Jul 24 07:29:28 UTC 2010


Gavin Hurlbut wrote:
> On Fri, Jul 23, 2010 at 4:56 PM, Kevin Ross <kevin at familyross.net 
> <mailto: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.
mythtv and bonnie are quite opposite applications. Reading large 
multimedia-files and reading/writing database-fields. What's good for 
one is really bad for the other.
The default for 'current' kernels are 1M for both r and w.
All nfs blocksizes have gone up over the last years and for a reason.
I myself use a special-kernel with 2M blocksizes.
>  
> 
>     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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> 
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