On Mon 10-08-09 18:42:05, Pavel Machek wrote: > On Tue 2009-08-11 14:57:03, Theodore Tso wrote: > > On Tue, Aug 11, 2009 at 05:29:14PM +0200, Andi Kleen wrote: > > > > Good to hear. I've so far stayed with data=ordered as I think I'd prefer > > > > data=guarded over data=writeback. I'll certainly give it a try when it's > > > > available. > > > > > > Same here. data=writeback already cost me a few files after crashes here :/ > > > > What sort of files were you losing? I don't know if we can improve > > the implied flush hueristics, but we should at least try to see if we > > do something about it. > > IIRC... the flush heuristics invoke async flush, so you can still lose > data if you are unlucky, no? Of course you can but it can happen in data=ordered mode as well (if the machine crashes before the transaction is committed). The percieved difference is in the fact that kjournald starts its commit every 5 seconds while pdflush starts writeback every 30-35 seconds. So if you use data=guarded/writeback mode and set dirty_expire_centisecs to 500, the experience wrt. data loss is going to be similar to data=ordered mode. fsync with heavy background writers won't be that painful as in data=ordered mode but apart from that the performance will be probably comparable. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
