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Tue, 29 Jan 2019 14:55:32 -0500 X-Greylist: delayed 488 seconds by postgrey-1.27 at vger.kernel.org; Tue, 29 Jan 2019 14:55:29 EST Received: from venice.bhome ([94.38.145.70]) by smtp-32.iol.local with ESMTPA id oZLqgOB5kMwWBoZLqg4F79; Tue, 29 Jan 2019 20:47:19 +0100 x-libjamoibt: 1601 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=libero.it; s=s2014; t=1548791239; bh=JJMolTMS8f1OyGF4DiebjbHo3W/psB6goX8nW2nV1u4=; h=Reply-To:Subject:To:Cc:References:From:Date:In-Reply-To; b=Al/2TE4hgHg4fRH2RSCy2F6QWnjGWNbUACsww0AYbs6YFd+wDhjFEer4A4llJHZ29 xK1oORxY0x1mhLQC62uVZht3dMIrjFrxSwfrUq4KrQL5K1SoDyXkQtuGiBihfvwyD3 MtXzxzfKHTlepNPYOxKky0KF5baBavzUNveQK7VfeuyNcgGW1NHe8eTsz6XqXraM1V Wx4PXUPKdnaZBompQmubYHccZaJZjjUn6AAAPX2j0forgF4Qj4vIEq6vDP/Mb7Butl qJ6F0i662C8kcG0DDIovne0Klz10t44ozAUqv4kYE+j71WAtMOkDMsiJ6SnVMBkGFk JsfxVLnauEkZg== X-CNFS-Analysis: v=2.3 cv=c6h6vi1l c=1 sm=1 tr=0 a=iMf660l5wNhVPkRQRjbP0g==:117 a=iMf660l5wNhVPkRQRjbP0g==:17 a=IkcTkHD0fZMA:10 a=4jqkTvAoAAAA:8 a=9r0XvWVT7kJZ7IYm-1MA:9 a=QEXdDO2ut3YA:10 a=Hh_HAVYRK2TLt7S9I1XE:22 Reply-To: kreijack@inwind.it Subject: Re: RAID56 Warning on "multiple serious data-loss bugs" To: Chris Murphy , Remi Gauvin Cc: DanglingPointer , linux-btrfs References: <5d7f63b2-d340-7c3a-679b-26e97ac258a6@gmail.com> <59a60289-1130-27b4-960b-9014fc8d68e8@gmx.com> <36be9ca6-4aa0-f00a-c1b4-a59026a1909e@georgianit.com> From: Goffredo Baroncelli Openpgp: preference=signencrypt Autocrypt: addr=kreijack@libero.it; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-CMAE-Envelope: MS4wfC6+q3eRr9gs6dZpsMHbVyipec5v7gGbLh9RkUgMUWnLHQELRK5tfcprJAC8eRzOxwnl1xnzku3tYq0OZypn3MhUjfnMpDeecEkuQTNcktzD5TUbWmJ7 c7rhsIOtVdKgzVGPxcyvlekCa9eKrocV1aGjsigV50yXqPe9cLcif0owBW/i2D97ADKtx2kuxbNVy9YA/lXF7NYGBjCi2bKkZz84kdOkTgA7/2osFwrJX2Eg OFDAkLuIWarzLoUyax5w89fnWsTp6mqvxYq+br7HnHIHrKOfrDotZmdyfAGz2yBY Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 29/01/2019 20.02, Chris Murphy wrote: > On Mon, Jan 28, 2019 at 3:52 PM Remi Gauvin wrote: >> >> On 2019-01-28 5:07 p.m., DanglingPointer wrote: >> >>> From Qu's statement and perspective, there's no difference to other >>> non-BTRFS software RAID56's out there that are marked as stable (except >>> ZFS). >>> Also there are no "multiple serious data-loss bugs". >>> Please do consider my proposal as it will decrease the amount of >>> incorrect paranoia that exists in the community. >>> As long as the Wiki properly mentions the current state with the options >>> for mitigation; like backup power and perhaps RAID1 for metadata or >>> anything else you believe as appropriate. >> >> Should implement some way to automatically scrub on unclean shutdown. >> BTRFS is the only (to my knowlege) Raid implementation that will not >> automatically detect an unclean shutdown and fix the affected parity >> blocks, (either by some form of write journal/write intent map, or full >> resync.) > > There's no dirty bit set on mount, and thus no dirty bit to unset on > clean mount, from which to infer a dirty unmount if it's present at > the next mount. It would be sufficient to use the log, which BTRFS already has. During each transaction, when an area is touched by a rwm cycle, it has to tracked in the log. In case of unclean shutdown, it is already implemented a way to replay the log. So it would be sufficient to track a scrub of these area as "log replay". Of course I am talking as not a BTRFS developers, so the reality could be more complex: e.g. I don't know how it would be easy to raise a scrub process on per area basis. BR G.Baroncelli -- gpg @keyserver.linux.it: Goffredo Baroncelli Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5