Network Overhead

VOV lets you distribute computation across the network without adding significant overhead. In some cases, it pays to be careful about the distribution of data and computation.

The following table shows the time it takes to archive the same 6.3MB Linux library using the same Linux CPU (called "reno") and varying the location of the modules and that of the target library.
CPU Modules Library Time
reno tahoe tahoe 1m42s
reno tahoe reno 47s
reno reno reno 5s
In all cases the network is a rather quiet standard 10BaseT Ethernet, the machine "tahoe" is a Sparc5/110 running Solaris2.5 (that is a sun5), and the command to build the library was of the type:
% ar rscv LIBRARYNAME.a *.o

Building the library across the network takes almost 2 minutes, while doing the same operation locally takes just 5 seconds. The difference is explained by extra disk and network traffic. Just copying the object files from the sun5 to the Linux box takes 29 seconds.

For other operations, such as linking of large binary files, the difference may be even more dramatic. The point is that, if you want speed, you must limit the network traffic. With VOV this is easy and can be made completely transparent to the end users.

You allocate disk space on various machines in the network and, as part of your design methodology, you include operations that move the data intelligently between the disks. It is easy to constrain some operations to be performed on the machine that physically owns the data; use the Job Editor and modify the Resources field. For example, if the Linux box with the disk space is called "reno," you can restrict selected tools to run on it by setting the Resources field to reno.