The openMosix File System (oMFS) is the filesystem used by openMosix kernels. You get it by installing an openMosix kernel on the nodes of your cluster with oMFS enabled in the kernel-config. (It should be enabled in the openMosix RPMs by default.)
You should also enable Direct Filesystem Access (DFSA) which allows a migrated process to execute many syscalls on the remote node locally without the need to migrate it back to its home node.
The use and administration of oMFS is very similar to NFS, but unlike NFS, oMFS features:
Cache consistency
Timestamp consistency
Link consistency
Please read more about oMFS and how to use it in earlier chapters of the HOWTO.
DFSA stands for Direct File System Access and is an optimization. It allows remote proccesses to perform some file system system calls locally rather then sending them to their home node. MFS stands for Mosix File System and allows all nodes access to all node filesystems. DFSA runs on top of a cluster filesystem, in this case MFS.