You can use the syncdir mount option for cluster file systems that use UFS as the underlying file system. However, performance significantly improves if you do not specify syncdir. If you specify syncdir, the writes are guaranteed to be POSIX compliant. If you do not specify syncdir, you experience the same behavior as in NFS file systems. For example, without syncdir, you might not discover an out of space condition until you close a file. With syncdir (and POSIX behavior), the out-of-space condition would have been discovered during the write operation. The cases in which you might have problems if you do not specify syncdir are rare.