From: "Martin K. Petersen" Subject: Re: I/O topology fixes for big physical block size Date: Tue, 28 Sep 2010 17:24:56 -0400 Message-ID: References: <1285605664-27027-1-git-send-email-martin.petersen@oracle.com> <4CA0CC38.5010804@fusionio.com> <4CA118FF.1080100@fusionio.com> <20100927231551.GA15653@redhat.com> <4CA16F6A.1090904@fusionio.com> <4CA17B13.7080801@redhat.com> <20100928141545.GA21587@redhat.com> <20100928205741.GA22257@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mike Snitzer , Eric Sandeen , Jens Axboe , "Martin K. Petersen" , "James.Bottomley\@hansenpartnership.com" , "linux-scsi\@vger.kernel.org" , "linux-ext4\@vger.kernel.org" To: "Ted Ts'o" Return-path: Received: from rcsinet10.oracle.com ([148.87.113.121]:55867 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753600Ab0I1V0r (ORCPT ); Tue, 28 Sep 2010 17:26:47 -0400 In-Reply-To: <20100928205741.GA22257@thunk.org> (Ted Ts'o's message of "Tue, 28 Sep 2010 16:57:41 -0400") Sender: linux-ext4-owner@vger.kernel.org List-ID: >>>>> "Ted" == Ted Ts'o writes: Ted> Can we decide soon what the right thing should be? I'm about to Ted> release e2fsrogs 1.41.13, and if I should put in some sanity Ted> checking code so mke2fs does something sane when it sees a 1M Ted> physical block size, I can do that. I don't think it's entirely clear what the "right thing" would be. Let's ignore the 1MB block size for now. That's clearly a fluke and a buggy device. But there are SSDs that will advertise an 8KiB physical block size. And apparently 16KiB devices are in the pipeline. How do we want to handle these devices? Allowing blocks bigger than the page size is going to be painful. So the question is whether we can tweak the filesystem layout in a way that would alleviate the pain without having to change the filesystem block size in the traditional sense. At least we're talking about SSDs and arrays here. I assume the partial block write penalty for these devices would be smaller than it is for rotating media. -- Martin K. Petersen Oracle Linux Engineering