From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 787FFC10F00 for ; Sat, 16 Feb 2019 08:16:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45E00222DD for ; Sat, 16 Feb 2019 08:16:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="kvSGaqaO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726684AbfBPIQ1 (ORCPT ); Sat, 16 Feb 2019 03:16:27 -0500 Received: from aserp2130.oracle.com ([141.146.126.79]:36650 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726159AbfBPIQ1 (ORCPT ); Sat, 16 Feb 2019 03:16:27 -0500 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x1G8FQJl121099; Sat, 16 Feb 2019 08:16:19 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=rVac246B1RmfZmhxW/6km/K6xp8ZFbRMUyweMBZZHSc=; b=kvSGaqaOnNTsnGYOQiD150XlG0NKoHJdKIqq7LMZorl3s3E4AVldi5L5eT9+tUDrR+Zr dTLanMlGznmKC9NBzycnyEcU1JiylJpCEXLW2DNxmcy+Ki3hzc2WmPMGj6hCxJnYZwpE Ju6hSY/qgtMm48QpnrVbDgOALIgilXMBc3ZeiniWYrw9viiaOxKGwBErnHnlBXsedsfe 1HJL+1n4v7rpP3vP2b/sbFBs042+5ng2gLRxIfigptuRV14CDBP5nqA7UZ2Tq0EIpCUW ufuue30Xkq8Mxd5g/Vfx0IRREEXu1BdarolhUrddbuZlEjSIrnIGBBQPSGFUUv6WPYi+ Vw== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by aserp2130.oracle.com with ESMTP id 2qp81drkxh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 16 Feb 2019 08:16:19 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x1G8GIT9010072 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 16 Feb 2019 08:16:18 GMT Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x1G8GHq7001141; Sat, 16 Feb 2019 08:16:17 GMT Received: from [192.168.1.12] (/116.239.187.160) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sat, 16 Feb 2019 00:16:17 -0800 Subject: Re: [LSF/MM TOPIC] Software RAID Support for NV-DIMM To: Dave Chinner , Johannes Thumshirn Cc: lsf-pc@lists.linux-foundation.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-btrfs@vger.kernel.org, hare@suse.de References: <20190215095710.GA12279@linux-x5ow.site> <20190216053133.GT20493@dastard> <20190216053957.GU20493@dastard> From: Bob Liu Message-ID: Date: Sat, 16 Feb 2019 16:16:12 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190216053957.GU20493@dastard> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9168 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902160062 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2/16/19 1:39 PM, Dave Chinner wrote: > On Sat, Feb 16, 2019 at 04:31:33PM +1100, Dave Chinner wrote: >> On Fri, Feb 15, 2019 at 10:57:12AM +0100, Johannes Thumshirn wrote: >>> (This is a joint proposal with Hannes Reinecke) >>> >>> Servers with NV-DIMM are slowly emerging in data centers but one key feature >>> for reliability of these systems hasn't been addressed up to now, data >>> redundancy. >>> >>> While it would be best to solve this issue in the memory controller of the CPU >>> itself, I don't see this coming in the next few years. This puts us as the OS >>> in the burden to create the redundant copies of data for the users. >>> >>> If we leave of the DAX support Linux' software RAID implementations (MD, >>> device-mapper and BTRFS RAID) do already work on top of pmem devices, but they >>> are incompatible with DAX. >>> >>> In this session Hannes and I would like to discuss eventual ways how we as an >>> operating system can mitigate these issues for our users. >> >> We've supported this since mid 2018 and commit ba23cba9b3bd ("fs: >> allow per-device dax status checking for filesystems"). That is, >> we can have DAX on the XFS RT device indepently of the data device. >> >> That is, you set up pmem in three segments - two small identical >> segments start get mirrored with RAID1 as the data device, and >> the remainder as a block device that is dax capable set up as the >> XFS realtime device. Set the RTINHERIT bit on the root directory at >> mkfs time ("-d rtinherit=1") and then all the data goes to the DAX >> capable realtime device, and all the metadata goes to the software >> raided pmem block devices that aren't DAX capable. >> >> Problem already solved, yes? > > Sorry, this was meant to be a reply to Dan's email commenting about > some people needing mirrored metadata, not the parent that was > talking about whole device RAID... > > i.e. mirrored metadata w/ FS-DAX for data should already be a solved > problem... > Indeed, here is the v2 version about mirrored metadata retry. https://marc.info/?l=linux-block&m=155005161104512&w=2 Appreciate any reviews, thank you! - Bob