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Ordered/Writeback mode questions



Some more dumb question, assuming I was using writeback mode and I made
a series of inserts into a database (not neccasary a database
transaction), my understanding is if the machine rebooted between
inserts, I couldn't gurantee if the data actually was on disk or not
even though the database server could have returned an okay saying it
got an okay from the filesystem (assuming I have write-caching on disk
disabled)

Now, if I were to use ordered mode. Everything would be in the right
place on the disk in the above scenario.

Or I have missed something ?


> 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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