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Re: Overwrite Mechanism

On 2010-02-24, at 01:49, Schrittesser, Florian wrote:
i wanted to ask you all about the exact overwrite mechanism used in ext3; is the information in the datablocks overwritten or written to a new location and the information in the referring inode is changed? Is it depending on the application used (and the functions it calls) or independent from that?

Please don't hesitate to go into further details and thanks for your help!

It depends on what your application is doing. If it is opening the file with open(O_TRUNC) then writing it, the new data is written to wherever it is allocated. If O_TRUNC is not used, then the data is written into the same blocks as were previously allocated to the file.

Cheers, Andreas
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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