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=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 424E2C4646D for ; Sat, 4 Aug 2018 16:22:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC03B217CD for ; Sat, 4 Aug 2018 16:22:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=thunk.org header.i=@thunk.org header.b="DgAbyfh8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CC03B217CD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mit.edu 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 S1728835AbeHDSX0 (ORCPT ); Sat, 4 Aug 2018 14:23:26 -0400 Received: from imap.thunk.org ([74.207.234.97]:37572 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727788AbeHDSX0 (ORCPT ); Sat, 4 Aug 2018 14:23:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=thunk.org; s=ef5046eb; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=IFMoixiTCQw0hSTWrxKp8kT6byCt9H6gEhDcDQM//Vk=; b=DgAbyfh8A/Pn4IhWT/kGtJQgzF 9IHWm3OUg/YpQdw2InXrskMeI/YmaXN2RsGZuj+rEhWJQsdjUmqen9Asu9/jSIvIh1w1nBAobm7Xn IeO5J/zFMm50ANryOpg7wF4U2Jd1W9QOheQ46BgIGA44lYStGP6x+g5b5VShR67GWt70=; Received: from root (helo=callcc.thunk.org) by imap.thunk.org with local-esmtp (Exim 4.89) (envelope-from ) id 1flzJe-0000Pz-HU; Sat, 04 Aug 2018 16:22:06 +0000 Received: by callcc.thunk.org (Postfix, from userid 15806) id 9CD3B7A64C9; Sat, 4 Aug 2018 12:22:05 -0400 (EDT) Date: Sat, 4 Aug 2018 12:22:05 -0400 From: "Theodore Y. Ts'o" To: Zdenek Kabelac Cc: Mike Snitzer , Linus Torvalds , Jens Axboe , Sagi Grimberg , Linux Kernel Mailing List , linux-block , dm-devel@redhat.com, Ilya Dryomov , wgh@torlan.ru Subject: Re: [dm-devel] LVM snapshot broke between 4.14 and 4.16 Message-ID: <20180804162205.GB4461@thunk.org> Mail-Followup-To: "Theodore Y. Ts'o" , Zdenek Kabelac , Mike Snitzer , Linus Torvalds , Jens Axboe , Sagi Grimberg , Linux Kernel Mailing List , linux-block , dm-devel@redhat.com, Ilya Dryomov , wgh@torlan.ru References: <1ec0a220-d5b0-1c27-e63b-c4d3f4ce9d77@torlan.ru> <20180803185431.GB3258@redhat.com> <20180803193037.GA4581@redhat.com> <20180804052033.GA4461@thunk.org> <102c2d75-f768-a649-52c3-bac6f0ca738d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <102c2d75-f768-a649-52c3-bac6f0ca738d@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 04, 2018 at 10:36:50AM +0200, Zdenek Kabelac wrote: > dm-snapshost has really outdated design - it's been useful in the old age > where megabyte was hell lot of space. > > Nowadays, when users do need to handle snapshots in multi gigabyte sizes and > moreover have number of snapshots from the same volume taken over the time, > want to take snapshot of snapshot of snapshot, the old snapshot simple kills > all the performance, uses tons of resources and becomes serious bottleneck > of your system and has lots of usability limitation. Fair enough. I don't think I would consider that makes dm-snapshot a "steaming pile". For me, protection against data loss is Job One. > That's where thin provisioning will shine.... The dm-thin development might want to take a look at what's currently in Documentation/device-mapper/thin-privisioning.txt: Status ====== These targets are very much still in the EXPERIMENTAL state. Please do not yet rely on them in production. But do experiment and offer us feedback. Different use cases will have different performance characteristics, for example due to fragmentation of the data volume. If you find this software is not performing as expected please mail dm-devel@redhat.com with details and we'll try our best to improve things for you. Userspace tools for checking and repairing the metadata are under development. Saying that dm-snapshot is a steaming pile and dm-thin is what everyone should use doesn't seem to be consistent with the above. Cheers, - Ted