From: Roman Mamedov <rm@romanrm.net>
To: Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: Unable to open ctree
Date: Mon, 3 Oct 2016 01:22:25 +0500 [thread overview]
Message-ID: <20161003012225.089c4d38@natsu> (raw)
In-Reply-To: <CAJCQCtTr3tG_8YSB_8gfBkpy558HKC+cz394B0wH2Je3v9kZmQ@mail.gmail.com>
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On Sun, 2 Oct 2016 13:29:56 -0600
Chris Murphy <lists@colorremedies.com> wrote:
> Well short of a bug, the problem aren't the checksums. The problem is
> the metadata is wrong, so if you recalculate checksums you're likely
> end up with an even more corrupted file system because it'll start out
> trusting bad metadata.
It appears that metadata got created with profile "single", because the device
is SSD. If this was DUP metadata, this entire problem wouldn't happen.
It is a terrible idea to downgrade metadata to single on detecting SSDs at
mkfs. The original rationale was that "SSDs will deduplicate it anyways", but
there are many ways things can corrupt way before reaching the SSD (from the
point of view of which it will look like the computer sent two different
metadata blocks, if one got corrupted in flight), and secondly, the ability of
SSDs to perfectly deduplicate small 4K sized pieces of data at hundreds of
megabytes in read/write speeds is VASTLY overestimated here.
--
With respect,
Roman
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next prev parent reply other threads:[~2016-10-02 20:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-02 18:17 Unable to open ctree Leonidas Spyropoulos
2016-10-02 19:29 ` Chris Murphy
2016-10-02 20:12 ` Leonidas Spyropoulos
2016-10-02 20:22 ` Roman Mamedov [this message]
2016-10-02 20:27 ` Chris Murphy
2016-10-02 22:05 ` Leonidas Spyropoulos
2016-10-02 20:46 ` Leonidas Spyropoulos
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