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Re: ordered vs full journaling mode



On Fri, Oct 10, 2003 at 11:17:58AM -0500, Vijayan Prabhakaran wrote:
> 
> Hi,
> 
> I was trying to list problems with ordered journaling mode that
> are not present in the full (data=journal) journaling mode. Please
> letme know if this is incorrect:
> 
> Assume that the following sequence of events take place:
> 
> 1. an already existing file A is deleted
> 2. new file B is created
> 3. blocks of A are allocated to B
> 4. blocks of B are written
> 5. inode of A & B are updated
> 
> In ordered data journaling mode, if the system crashes after writing
> the blocks of B but before updating the metadata of A (that is,
> between steps 4 and 5), then A might see spurious data. However this
> problem cannot happen if we have a full journaling mode.
> 
> Is the above example correct ? If not, could you please give me a
> situation where ordered data journaling mode will not give as much
> reliability as the full journaling mode ?

No, it's not correct.  Blocks belonging to deleted files will not be
re-allocated until the delete has been committed onto disk, precisely
to avoid this sort of spurious data condition.

						- Ted




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