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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5243C77B75 for ; Fri, 19 May 2023 10:21:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231821AbjESKVC (ORCPT ); Fri, 19 May 2023 06:21:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231812AbjESKVB (ORCPT ); Fri, 19 May 2023 06:21:01 -0400 Received: from out-52.mta1.migadu.com (out-52.mta1.migadu.com [95.215.58.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B41F01AD for ; Fri, 19 May 2023 03:20:59 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1684491657; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=f2/x6o647fvkKRQ4lSsMEFjqh2VPCvaHWpW8KsvuUhc=; b=udnu0OVvT3ytoawjOfIe1810YEwd+/YchbDwaeS9LLPAfJdSgSv7Fl97genyHxEdc96kNe EalU2SNzYTM70jEQB16CBfoI2denCGZHl/8Vm3EAphdtIBbbAf8Hb6oYHlI/qQ3sUE4lvz g+ULGmlGlNDa2YB2/gt54yw/v2xjMF4= Date: Fri, 19 May 2023 18:20:47 +0800 MIME-Version: 1.0 Subject: Re: [PATCH for-next v5 0/7] On-Demand Paging on SoftRoCE Content-Language: en-US To: "Daisuke Matsuda (Fujitsu)" , "linux-rdma@vger.kernel.org" , "leonro@nvidia.com" , "jgg@nvidia.com" , "zyjzyj2000@gmail.com" Cc: "linux-kernel@vger.kernel.org" , "rpearsonhpe@gmail.com" , "Xiao Yang (Fujitsu)" , "Zhijian Li (Fujitsu)" , "Yasunori Gotou (Fujitsu)" References: <0f12adcd-0112-3b0e-57b5-ecf707670bc0@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Guoqing Jiang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 5/19/23 17:57, Daisuke Matsuda (Fujitsu) wrote: > On Fri, May 19, 2023 3:42 PM Guoqing Jiang wrote: >> Hello, >> >> On 5/18/23 16:21, Daisuke Matsuda wrote: >>> [2] [PATCH for-next v3 0/7] On-Demand Paging on SoftRoCE >>> https://lore.kernel.org/lkml/cover.1671772917.git.matsuda-daisuke@fujitsu.com/ >> Quote from above link >> >> "There is a problem that data on DAX-enabled filesystem cannot be >> duplicated with >> software RAID or other hardware methods." >> >> Could you elaborate a bit more about the problem or any links about it? >> Thank you. > I am not an expert of Pmems, but my understanding is as follows: > > Pmem (Persistent memory) is detected as memory device during boot process. > Physical addresses are allocated to them just like other memory in DIMM slots, > so system have to treat them differently from traditional storage devices like HDD/SSD. > > It may be technically possible to duplicate data using multiple Pmems, but the duplication > is practically not useful. For traditional storage devices, you can hot-remove and hot-add > them easily on failure. However, Pmems are not attached to hot-pluggable slots. You have > to halt the system and open the cabinet to change out the Pmem. This means availability > of the system is not improved with data duplication on the same host. I guess pmem with block translation table type would be fine since it can be used like normal storage device, but I am not pmem expert as well 😁. Thanks, Guoqing