mode data=journal in ext3. Is it safe to use?

Oleg Drokin green at
Fri Jun 18 10:15:20 UTC 2004


On Fri, Jun 18, 2004 at 11:41:23AM +0200, Helge Hafting wrote:

> >If you can reproduce a garbage in files in ordered journal mode, that 
> >would be a
> >bug that should be fixed then.
> Hard to _produce_, but consider:
> 1. Write data to an existing file
> 2. Sync metadata
> 3. data is forced out because of ordered mode, a powerout crash happens
>    in the middle of this. The file now has a block with a mix of new 
> and old,

Well, this is not much worse than having two blocks, one from old file
and one from new after a crash.

>    it may even be unreadable due to a bad sector checksum.

Well, in data journaled mode you may get unreadable journal, is this much
better? (Also original question was about CF flash media, so no bad sector
problems I presume).

> With data journalling you either get the old data (because the crash 
> happened
> during a write to the journal) or new data (crash happened during data 
> write,

Well, while with data journaling mode your granularity is one block,
with data ordered it is one sector.

> the data is restored from the good copy in the journal.)


More information about the Ext3-users mailing list