Unix File System

Let's consider developing DBMS using unix file systems. I have two questions. 1) If the O_SYNC option is available (System V release 4.0 provides), can the data that the DBMS manages be recovered after system crash ? Is there any problem about it ? If so, why do commercial DBMS's use the raw disk instead of a unix file system? If anyone have information about recovery scheme in DBMS using unix file system, please, let me know that. 2) If the large number of records are inserted, the Inode should use indirect mapping for addressing data pages. Is there any performance problems caused by this indirect mapping? How many entries are there in a Inode for direct mapping? ; i.e. the number of data pages that can be accessed by direct mapping. How many entries are there in a Inode for single indirect mapping? How many entries are there in a Inode for double indirect mapping? How many entries are there in a Inode for triple direct mapping? Please, let me know those. /**************************************************************/ /* Sang-Wook Kim Internet: wook@mozart.kaist.ac.kr */ /* Department of Computer Science, */ /* Korea Advanced Institute of Science and Technology (KAIST) */ /* 373-1 Kusong-dong, Yusong Taejon 305-701,Republic of Korea */ /* TEL: +82-42-869-3562 FAX: +82-42-869-3510 */ /**************************************************************/