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From: Goffredo Baroncelli <kreijack@libero.it>
To: Chris Murphy <lists@colorremedies.com>,
	Remi Gauvin <remi@georgianit.com>
Cc: DanglingPointer <danglingpointerexception@gmail.com>,
	linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: RAID56 Warning on "multiple serious data-loss bugs"
Date: Tue, 29 Jan 2019 20:47:17 +0100
Message-ID: <80f46e68-4cda-3a22-385b-0ab0a47b079a@libero.it> (raw)
In-Reply-To: <CAJCQCtQ=mGdZ+90uR68hwqFcZaNP8xQwKXkpO395xB+KBXRkxA@mail.gmail.com>

On 29/01/2019 20.02, Chris Murphy wrote:
> On Mon, Jan 28, 2019 at 3:52 PM Remi Gauvin <remi@georgianit.com> 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 <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-26 11:45 DanglingPointer
2019-01-26 12:07 ` waxhead
2019-01-26 14:05   ` Remi Gauvin
2019-01-28  0:52 ` Qu Wenruo
2019-01-28 15:23   ` Supercilious Dude
2019-01-28 16:24     ` Adam Borowski
2019-01-28 22:07   ` DanglingPointer
2019-01-28 22:52     ` Remi Gauvin
2019-01-29 19:02       ` Chris Murphy
2019-01-29 19:47         ` Goffredo Baroncelli [this message]
2019-01-30  1:41           ` DanglingPointer
2019-02-01 18:45         ` Remi Gauvin
2019-01-29  1:46     ` Qu Wenruo

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