ext3 and forced unit access to flush disk cache

Ric Wheeler ricwheeler at gmail.com
Wed Apr 13 19:34:08 UTC 2011

On 04/08/2011 06:51 PM, Mark Busheman wrote:
> I plan to use data=journal option with ext3 for a customer who is very
> specific about the integrity of the data. Would like to know if ext4
> send FUA (Forced Unit Access) to flush the disk cache?
> Cheers
> Mark

ext4 by default uses "barrier" support and will issue the write commands 
(depends on the storage type). You can "mount -o barrier" ext3 as well.

It will do this for its own metadata reasons and as part of an application 
driven fsync() command, so the customer data should be safe if their application 
is coded properly.



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