Re: EXT3 & EXT4 filesystems are NOT safe.

2009/3/26 Art Kagel <art.kagel@gmail.com>: > Friends, Colleagues, Clients: > > According to Linus Torvalds, Linux's EXT3 filesystem is not safe since it > writes its meta data to disk before committing the related data changes to > the file.  This can mean corrupted files if the system crashes between the > two non-atomic writes to disk.  About this EXT3 algorithm, Linus says: > "Whoever came up with that solution was a moron. No ifs, buts, or maybes > about it." Here's a non-Slashdot source of information - with pointers onwards: http://www.h-online.com/open/Kernel-developers-squabble-over-Ext3-and-Ext4--/news/112937 [...] > I hate to say I told you so, but I have continued to recommend that IDS > chunks ONLY use RAW devices and NOT filesystems all along, even since the > incorporation of DIRECT IO support in IDS.  If you MUST use COOKED chunks, > and with Linus still trying to get rid of RAW altogether, we may not have a > choice at some point, at least use COOKED device files NOT filesystem files. Basically sound. The problem for IDS is that it assumes that when the write() call returns, the data is safely on disk. If the data is not safe, all bets are off. And the more software there is between IDS and the disks, the less reliable the result tends to be. -- Jonathan Leffler #include <disclaimer.h> Email: jleffler@earthlink.net, jleffler@us.ibm.com Guardian of DBD::Informix v2008.0513 -- http://dbi.perl.org/ "Blessed are we who can laugh at ourselves, for we shall never cease to be amused." NB: Please do not use this email for correspondence. I don't necessarily read it every week, even. Mercedes McCambridge - "I'd never been in play long enough for the flowers to die in the dressing room."

Jonathan Leffler wrote: > And the more software there is between IDS > and the disks, the less reliable the result tends to be. > Not just S/W. Disk drives can have buffers larger than an Informix chunk. -- Ian Hotmail is for spammers. Real mail address is igoddard at nildram co uk