From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clements Subject: Re: Linux MD RAID5/6 bitmap patches Date: Wed, 22 Mar 2006 13:06:48 -0500 Message-ID: <44219238.9080905@steeleye.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Yogesh Pahilwan Cc: 'Neil Brown' , linux-raid@vger.kernel.org List-Id: linux-raid.ids Yogesh Pahilwan wrote: > Thanks for your reply. As far as what I understood that when we apply the > bitmap patch, for every write it will do 2 sync writes that is setting the > dirty bit, writing intent log and one async write for clearing the dirty > bit. Is it correct? The bits are in the intent log, so the "setting dirty bit" and "writing intent log" are the same thing. Just one write. > If that is the case are there any patches available which can do collection > of sync write in a queue and write a collection in single write request. > For Eg: > For 10 writes , we will have 10 + 1 sync writes + 10 async write. The bitmap code already does this by default. The bitmap writes are queued up so that all writes to a given page (within a short time period) are reduced to a single write. The performance is actually quite good. There's very little performance difference between having a bitmap versus not having one. > I mean to say , 10 sync writes for setting the dirty bits + 1 sync write for > write intent log for all queued request in one write operation + 10 async > write for clearing the dirty bit. The async writes for clearing the bitmap are also combined. -- Paul