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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 DC3B7ECDE46 for ; Thu, 25 Oct 2018 21:52:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 95B002083E for ; Thu, 25 Oct 2018 21:52:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95B002083E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=youngman.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727706AbeJZG1R (ORCPT ); Fri, 26 Oct 2018 02:27:17 -0400 Received: from smtp.hosts.co.uk ([85.233.160.19]:38782 "EHLO smtp.hosts.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726174AbeJZG1Q (ORCPT ); Fri, 26 Oct 2018 02:27:16 -0400 X-Greylist: delayed 2236 seconds by postgrey-1.27 at vger.kernel.org; Fri, 26 Oct 2018 02:27:16 EDT Received: from [81.157.153.73] (helo=[192.168.1.82]) by smtp.hosts.co.uk with esmtpa (Exim) (envelope-from ) id 1gFmyi-0005Bd-Ac; Thu, 25 Oct 2018 22:15:40 +0100 Subject: Re: [RFC] dm-bow working prototype To: Paul Lawrence References: <20181023212358.60292-1-paullawrence@google.com> Cc: dm-devel@redhat.com, Linux kernel , linux-raid@vger.kernel.org From: Wols Lists Message-ID: <5BD2327B.1040908@youngman.org.uk> Date: Thu, 25 Oct 2018 22:15:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/10/18 19:13, Paul Lawrence wrote: >> I have some questions about dm-bow: >> – How file system agnostic this feature is planned to be? While it is >> designed with ext4 in mind, is it going to work when used over other >> file systems, like FAT or BTRFS for example? > So long as the file system supports fstrim, it should work. If the file > system creates a lot of churn say by running garbage collection, I'd not > recommend it. And I really don't see the use case if the file system has > any sort of snapshot capability - that will always be a superior > solution to a block level one IMO. Sorry for being dense, but why is this posted to linux-raid, then? Raid does not support fstrim, and is filesystem-agnostic. I can imagine people here being interested, but it feels to me as though your functionality is completely orthogonal to raid. Sorry. Cheers, Wol