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Re: Howto create hidden journal on / fs



Hi,

On Fri, Aug 03, 2001 at 10:27:21PM +0800, Yusuf Goolamabbas wrote:

> Stephen, Could you elaborate on the relaxed semantics. What should one
> look for in semantics of various ext3 modes (obviously depends on the
> workload) when deciding which mode to use
> 
> Andrew mentioned that in writeback mode, the contents of the file may
> have potentially stale data. What's the time window on this ?

writeback mode basically behaves the same as ext2.  Metadata gets
flushed to disk quickly, but data will be flushed only within a 30
second window.  If you reboot while metadata describing new data has
been written but the data has not, you'll see old disk blocks.  The
window there is the same as for ext2: you've got typically a 30 second
window after creating a new file where a reboot might show old data.

ordered mode never has this window, but for databases, you are usually
only writing to existing files, not creating new ones, so you probably
won't care about the difference between the two modes if that's your
workload.

Cheers,
 Stephen





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