NFS and slow links

[Marcus J. Ranum]

dsamperi at Citicorp.COM (Dominick Samperi) writes:

>[...] Further investigation
>revealed that what made all of the difference was whether or
>not the user's home directory was local or NFS-mounted. More
>precisely, the performance hit resulted from the need to write
>the output executable file (about 10Megs) to an NFS-mounted
>directory.

	This is because NFS writes are done synchronously - IE: the
calling process waits until the write has been performed on the server
before it returns. You can somewhat offset the damage by running the
block I/O demon on the client (biod(8)) but as long as you have to
do NFS writes you'll see some performance loss. Another approach some
take is to add battery-backed RAM caches to machines, to speed up
synchronous writes on the servers, thereby speeding up the clients
as well. Legato's PrestoCache (available for a variety of machines,
available as a built-in on some DEC servers) can speed NFS performance
up to 300% in some cases.

mjr.