From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id C4012139000 for ; Fri, 30 Jul 2021 14:30:15 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id A8F40E0933; Fri, 30 Jul 2021 14:30:08 +0000 (UTC) Received: from mail-oi1-f170.google.com (mail-oi1-f170.google.com [209.85.167.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id CB619E0918 for ; Fri, 30 Jul 2021 14:30:07 +0000 (UTC) Received: by mail-oi1-f170.google.com with SMTP id a19so13440102oiw.6 for ; Fri, 30 Jul 2021 07:30:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=g8156Mz5KVLSt5AOUiARAzRmJ9fqzF/tputQpmz9gwo=; b=h/KRp6SgF+2o++xrQvLKnf6bBnVCl361vcwM7tP0YWsTVy6+ng7rMJqFsUs0u7zV/P PZ0ARQhpczrnmn3DF38+KadmQw7NmPrk1GMdXyufmTkFW3s4EYDl9QYJsEeqB8X0YjX/ mKgudztZPtpLps0lNtomJBS7Fm49MNfmrnmc1Izb4Np0FG0iGzidpVueLEUpG2rUXF/Z wmjx/Izd9az7jGUdr1xrHTevKZHXLJGI7oD3FvsUGfgc0NxyYurOMj26XO17O0uySUxq 6h5or3LLG7TZdrY7A0zwrDayjv83pPfsTv8P+Q/79AOcHivuu5l5gaREFHQgz2QggMVK RGhA== X-Gm-Message-State: AOAM5317SFuR0+t3mSLIc/bQtm6PB3b2+Fogg2t6+RIcwefAMAx6sbjJ wyhbzx4f/9Lgnne5aUxfL0MPzq9h9C3Hu6pdBsOvu+SG X-Google-Smtp-Source: ABdhPJxtPjWj9qqgDpAOTqmyz9aYMJ4MS2LTJsGAFfzmgees+66fbHQ5nnauWEIbpXctDKv2t289eiORopjHooX5HP4= X-Received: by 2002:a05:6808:218f:: with SMTP id be15mr2026463oib.75.1627655406652; Fri, 30 Jul 2021 07:30:06 -0700 (PDT) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply MIME-Version: 1.0 References: <9946c2eb-bb5c-a9c0-ced9-1ac269cd69a0@gmail.com> <6ecbf2d6-2c6f-3f66-5eee-f4766d5e5254@gmail.com> <24805.48814.331408.860941@tux.local> <5483630c-3cd1-bca2-0a6d-62bb85a5adc6@gmail.com> <96fc901a-2ce4-0ea0-0ed1-1c529145c0e9@gmail.com> <6102DB58.7040103@youngman.org.uk> <56d64f52-1b9a-1309-c720-06bb63c9f80a@iinet.net.au> In-Reply-To: <56d64f52-1b9a-1309-c720-06bb63c9f80a@iinet.net.au> From: Rich Freeman Date: Fri, 30 Jul 2021 10:29:54 -0400 Message-ID: Subject: Re: [gentoo-user] [OT] SMR drives (WAS: cryptsetup close and device in use when it is not) To: gentoo-user@lists.gentoo.org Content-Type: text/plain; charset="UTF-8" X-Archives-Salt: a571a2ab-b21e-4745-8054-2f6c2ed649e7 X-Archives-Hash: e34eebb64834faba6507645c4dfd5f6e On Fri, Jul 30, 2021 at 1:14 AM William Kenworthy wrote: > > 2. btrfs scrub (a couple of days) > Was this a read-only scrub, or did this involve repair (such as after losing a disk/etc)? My understanding of SMR is that it is supposed to perform identically to CMR for reads. If you've just recently done a bunch of writes I could see there being some slowdown due to garbage collection (the drive has a CMR cache which gets written out to the SMR regions), but other than that I'd think that reads would perform normally. Now, writes are a whole different matter and SMR is going to perform terribly unless it is a host-managed drive (which the consumer drives aren't), and the filesystem is SMR-aware. I'm not aware of anything FOSS but in theory a log-based filesystem should do just fine on host-managed SMR, or at least as well as it would do on CMR (log-based filesystems tend to get fragmented, which is a problem on non-SSDs unless the application isn't prone to fragmentation in the first place, such as for logs). Honestly I feel like the whole SMR thing is a missed opportunity, mainly because manufacturers decided to use it as a way to save a few bucks instead of as a new technology that can be embraced as long as you understand its benefits and limitations. One thing I don't get is why it is showing up on all sorts of smaller drives. I'd think the main application would be for large drives - maybe a drive that is 14TB as CMR could have been formatted as 20TB as SMR for the same price, and somebody could make that trade-off if it was worth it for the application. Using it on smaller drives where are more likely to be general-purpose is just going to cause issues for consumers who have no idea what they're getting into, particularly since the changes were sneaked into the product line. Somebody really needs to lose their job over this... -- Rich