[mythtv-users] Re: Samba 3 better than NFS 3 for recording over Ethernet

Michael T. Dean mtdean at thirdcontact.com
Thu Dec 29 10:50:12 EST 2005

Mike Frisch wrote:

> On 29-Dec-05, at 3:19 AM, John Andersen wrote:
>> On 12/28/05, Mike Frisch <mfrisch at isurfer.ca> wrote:
>>> At least the following NFS mount options should be used if not  
>>> already:
>>> mount -o rsize=32768,wsize=32768,nfsvers=3,tcp server:/nfs/export /
>>> local/mountpoint 
>> On my slave I mount nfs with read/write sizes of 8192, which I  think 
>> I got
>> from the mythtv docs at
>> http://www.mythtv.org/docs/mythtv-HOWTO-23.html#ss23.10
>> Would you expect see any improvement with larger sizes on a 100meg
>> network?
> Yes. 

If supported by your NFS server's kernel (and NFS version--but that 
shouldn't be a problem)...

The maximum theoretical block size for NFSv2 is 8KiB (but you want 
NFSv3), and Linux 2.4 kernels without support for NFS over TCP (pre 
2.4.19) use 8KiB, while those 2.4 kernels that didn't support NFS over 
TCP but were patched with the NFS over TCP patch use 32KiB and those 
that support NFS over TCP without patching use 8KiB (the "traditional" 
default was kept even after the TCP patch was included in the tree).  
Linux 2.6 kernels support 32KiB block sizes by default.  However, your 
distribution vendor may have modified the kernel defaults.  The maximum 
theoretical sizes for NFSv3 are 56KiB over UDP and depends on the 
implementation with TCP (but typically won't be greater than 32KiB).

You can check your kernel by looking at the value for NFSSVC_MAXBLKSIZE 
in the include/linux/nfsd/const.h file in your kernel source directory.  
You can also modify the value and recompile your kernel to get better 

See http://tldp.org/HOWTO/NFS-HOWTO/performance.html#BLOCKSIZES and 
http://nfs.sourceforge.net/ for more.


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