[Linux-cluster] gfs export over nfs is very slow

[Wendy Cheng]

Try these:

1) Note that 2.6 kernel defaults NFS export option to "sync". So unless
you have a strong need, explicitly set NFS export to "async" in your
export file (/etc/exports in Red Hat systems) and do *not* mount NFS
shares with "sync" option.

2) Upon large NFS append (i.e. "write" that will increase file size),
using bigger block size (e.g. when using dd command) and/or bigger
application buffer AND increasing NFS wsize and rsize (mount option) to
its maximum, *if* you have to use "sync" in as either export or mount
option.

The problem here could be GFS sync due to its cluster filesystem nature
and its file sync design. So try to avoid it if possible.

Let us know how it goes. 

-- Wendy