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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 9111EC4646F for ; Sat, 4 Aug 2018 18:18:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52112217CB for ; Sat, 4 Aug 2018 18:18:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 52112217CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1729060AbeHDUUT (ORCPT ); Sat, 4 Aug 2018 16:20:19 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42410 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728054AbeHDUUT (ORCPT ); Sat, 4 Aug 2018 16:20:19 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0249D401B1F4; Sat, 4 Aug 2018 18:18:48 +0000 (UTC) Received: from localhost (unknown [10.18.25.149]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A29EF2026D66; Sat, 4 Aug 2018 18:18:47 +0000 (UTC) Date: Sat, 4 Aug 2018 14:18:47 -0400 From: Mike Snitzer To: "Theodore Y. Ts'o" Cc: Zdenek Kabelac , Linus Torvalds , Jens Axboe , Sagi Grimberg , Linux Kernel Mailing List , linux-block , dm-devel@redhat.com, Ilya Dryomov , wgh@torlan.ru Subject: Re: LVM snapshot broke between 4.14 and 4.16 Message-ID: <20180804181845.GA10499@redhat.com> 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> <20180804162205.GB4461@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180804162205.GB4461@thunk.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Sat, 04 Aug 2018 18:18:48 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Sat, 04 Aug 2018 18:18:48 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'msnitzer@redhat.com' RCPT:'' 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 12:22pm -0400, Theodore Y. Ts'o wrote: > 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. What's your point Ted? Do you have _any_ intention of actually using anything DM or is this just a way for you to continue to snipe at it? > > 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. Maybe read your email from earlier today before repeating yourself: https://lkml.org/lkml/2018/8/4/366