Re: Is file system based database reliable ?

On Thu, Feb 11, 1999 at 01:55:11AM +0000, David Williams wrote: > In article <36C09B4A.6248@bloomberg.net>, Art S. Kagel > <kagel@bloomberg.net> writes > >Tim Kutergin wrote: > >> > >> Hi all ! > >> Sorry for silly question: how reliable is Informix database implemented as > >> cooked files ? Documentation says that it is less reliable that raw > >> devices, since database could not guarantee writing to the media - > >> nonsense, there is fsync(2) system call and O_SYNC flag for open(2). At > >> least Oracle did not make such statement. Raw devices in Oracle are using > >> for enhanced performance and for special environments such as Parallel > >> Server. I am evaluating IDS usage in Linux environment but I afraid that > >> database reliability will be low (Linux does not support raw devices). > > > >No that reliability stuff is an old documentation holdover from Ver 1.2 > >which has never been corrected. IDS DEFINITELY opens cooked files in > >O_SYNC mode and your data is perfectly safe as long as the OS drivers > >and library properly implement that flag. The ONLY problem with using > >cooked files for Informix is that performance is about 15% better with > >RAW devices. > > > > I thought sometimes O_SYNC only guarantees metadata will be written o > the drive, not necessarily the actual data blocks themselves... man open O_SYNC When opening a regular file, this flag affects subsequent writes. If set, each write(S) waits for both the file data and file status to be physically updated. Kind Regards, Octav > > >Art S. Kagel > > -- > David Williams -- Octav Chiriac Phone: (373) 2 21 20 96 NetInfo S.R.L. Fax: (373) 2 21 36 59 Chisinau (373) 2 24 00 83 Moldova, Republic of mailto:com@netinfo-moldova.com