RFC: increasing NFS server max I/O size to 128K

Rick Macklem rmacklem at uoguelph.ca
Tue Apr 14 22:48:35 UTC 2015


Hi,

mav@ has suggested that 128K will provide better performance
for NFS servers using ZFS, since 128K is the default block size
used by ZFS.

I can't see any reason why changing the NFS server's maximum
I/O size from 64K->128K will cause problems.
However, if you think there will be issues related to this,
please let us know.

Note that the FreeBSD NFS client will still use 64K, because
changing the client is more problematic, due to its use of the
buffer cache. (I will be proposing a patch that will allow buffer
cache sizing to be architecture dependent, but that's not this post.;-)

The actual patch I have renames NFS_MAXDATA (which is the NFS server's
maximum I/O size) to NFS_SRVMAXIO for a couple of reasons:
1 - I wanted the name to make it clear that it applies to the server
    side only.
2 - I want the name to be different from the NFS_MAXDATA defined in
    /usr/include/rpcsvc/nfs_prot.h, which has nothing to do with the
    one defined in the kernel for the NFS server.

Any comments/concerns? rick


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