1. 512 bytes is the disk sector size, used in disk space allocation, irrelevant in this context. Filesystem block size in the context of Oracle performance tuning usually refers to the size of an I/O operation chunk. It is relevant. 2. Because of the inadequacy of df -g on Solaris, Veritas filesystem block size should only be checked with fstyp command, not df -g. See http://www.symantec.com/business/support/index?page=content&id=TECH8994 3. vxfs default block size depends on the filesystem size, just as Linux does. 4. If you intend to create an Oracle database on Windows, the NTFS filesystem block size has no effect on I/O performance, because Oracle on Windows uses direct I/O. (Oracle's decision may be due to the fact that before Vista, Windows limits filesystem I/O size to 64K. See http://technet.microsoft.com/en-us/magazine/2007.02.vistakernel.aspx ) 5. fstyp or newfs or other commands find the filesystem block size in a "static" manner. In operation, you can find this size by iostat or sar -d. The value of an I/O in bytes or kilobytes per second divided by the number of I/O's per second gives this value. See http://groups.google.com/group/comp.databases.oracle.server/msg/69ff44b368a2c424 for an example on Linux. 6. In case the memory page size differs from filesystem block size, I/O chunk size is still filesystem block size. See the above example again.