From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: asynchronous write Date: Thu, 19 Jul 2007 21:41:14 +1000 Message-ID: <18079.19930.835893.78600@notabene.brown> References: <200707180824.l6I8O7Ik006820@betty.it.uc3m.es> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Peter T. Breuer on Wednesday July 18 Sender: linux-raid-owner@vger.kernel.org To: ptb@inv.it.uc3m.es Cc: linux raid List-Id: linux-raid.ids On Wednesday July 18, ptb@inv.it.uc3m.es wrote: > Did the asynchronous write stuff (as it was in fr1) ever get into kernel > software raid? Hmmm... what was 'fr1' again??.. asks google. http://www.it.uc3m.es/ptb/fr1/ Yes, that sound like the 'bitmap' support currently in md. The bitmap is stored on disk which I think is different from what fr1 did. Possibly having a volatile bitmap would be valuable. It would remove the current extra cost of writes, and would still allow fast recovery if you fail, then re-add a drive... > > I see from the raid acceleration ("ioat") patching going on that some > sort of asynchronicity is being contemplated, but blessed if I can make > head or tail of the descriptions I've read. It looks vaguely like > purely memory-management stuff to me (what?) for external hardware raid, > but what do I know ... Yes. The ,'ioat' is for raid5/6 and allows the xor calculation, memcpys and some other functions to be off-loaded to a co-processor. NeilBrown