Thanks Ted for replying. >> FUA doesn't cause a cache flush. Thanks for correcting. Yes FUA does not flush cache. When the FUA bit is set in the write command, the drive make sure that the data goes to platters and not to be put into its cache for latter writes. >> Ext4 does send cache flush commands, or barriers, to make sure the data written to disk >> is flushed all the way down to the disk platters on transaction commits. I have few questions on this and need help: a. To achieve the above, is any specific options that need to be used while mounting? b. Are the above mentioned things done only for data=journal or for other modes such as data=ordered and writeback? c. Are they done for metadata, journal and data writes? d. Can I know what are the commands sent to the drives to do the cache flush commands or barriers? Would like to find if the drive support the commands? e. Is the above true also for ext3 - I posted a similar question to ext3 forum and have got no response so far? Cheers Mark On Sun, Apr 10, 2011 at 5:17 AM, Theodore Tso <tytso@xxxxxxx> wrote: > > On Apr 8, 2011, at 6:02 PM, Mark Busheman wrote: > >> I plan to use data=journal option with ext4. Would like to know if >> ext4 send FUA (Forced Unit Access) >> to flush the disk cache? > > FUA doesn't cause a cache flush. Ext4 does send cache flush commands, or barriers, to make sure the data written to disk is flushed all the way down to the disk platters on transaction commits. > > -- Ted > > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
