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CRDSS <br />TASK MEMORANDUM 1.05-25 <br />Study of System Integration Issues <br />System - Network File System Use in CRDSS <br />1.0 ISSUE <br />The CRDSS must use Network File System (NFS) software to allow the CRDSS machines to <br />transparently share hard disks. Several issues must be documented related to the use of NFS in <br />CRDSS: <br />To what extent will NFS be used? <br />? <br />What will be the structure for implementing NFS? <br />? <br />What are the limitations of NFS? <br />? <br />2.0 DISCUSSION/ANALYSIS <br />RTi has used NFS to connect machines involved in the development of large software projects. CSU <br />routinely uses NFS to make user accounts available on all machines in the engineering network. RTi <br />personnel who have worked in computing centers both in public and private organizations have <br />formulated procedures for implementing NFS in a software development environment. <br />The purpose of NFS is to make files from one machine available to other machines by "exporting" a <br />directory. Often, the directory that is exported is the top of a disk partition. Machines that have <br />access to the exported directory can "mount" the directory at any place on the local system. All <br />machines in a network should generally appear to have the same directory structure while <br />maintaining only one copy of each file in the network. This allows users to log in on any machine <br />and be presented with the same user environment. Each user should only have one account within a <br />network rather than having an account on each machine. If file space on one machine becomes tight, <br />the "home" of some users can be moved to a different machine, but they can still have access to all of <br />the machines. <br />Several methods can be used to implement NFS. Consider the example of having a directory called <br /> on the network. One way of making this directory available to machines using NFS is to <br />/crdss <br />create a directory (and/or partition) on one machine and export the directory to other <br />/crdss <br />machines on the network. Other machines then create a local mount point called and <br />/crdss <br />mount the main directory at this directory. This method has the advantage that it is the simplest, but <br />it is also not very flexible. One problem with this configuration arises when machines from different <br />manufacturers share files and therefore need to maintain separate executable programs and libraries. <br />In the example described above, each machine would need a separate directory (for <br />/crdss/bin <br />executables). However, NFS does not allow inclusive directories to be exported (e.g., both <br />/crdss <br />and cannot be exported, unless they are on separate disks). This limitation points to <br />/crdss/bin <br />the second alternative described below as being the best NFS configuration alternative. <br />1 <br />A275 05.10.94 1.05-25 Malers <br />