Re: Problem with file system

From: Marat Khalili <mkh@rqc.ru>
To: Chris Murphy <lists@colorremedies.com>, Dave <davestechshop@gmail.com>
Cc: Linux fs Btrfs <linux-btrfs@vger.kernel.org>,
	Fred Van Andel <vanandel@gmail.com>
Subject: Re: Problem with file system
Date: Tue, 31 Oct 2017 08:57:42 +0300	[thread overview]
Message-ID: <10fb0b92-bc93-a217-0608-5284ac1a05cd@rqc.ru> (raw)
In-Reply-To: <CAJCQCtS9BPZn-hnS+wP7Eu3oHQP_tS8EEM4j4FQDwRmzcFH+_A@mail.gmail.com>

On 31/10/17 00:37, Chris Murphy wrote:
> But off hand it sounds like hardware was sabotaging the expected write
> ordering. How to test a given hardware setup for that, I think, is
> really overdue. It affects literally every file system, and Linux
> storage technology.
>
> It kinda sounds like to me something other than supers is being
> overwritten too soon, and that's why it's possible for none of the
> backup roots to find a valid root tree, because all four possible root
> trees either haven't actually been written yet (still) or they've been
> overwritten, even though the super is updated. But again, it's
> speculation, we don't actually know why your system was no longer
> mountable.
Just a detached view: I know hardware should respect ordering/barriers 
and such, but how hard is it really to avoid overwriting at least one 
complete metadata tree for half an hour (even better, yet another one 
for a day)? Just metadata, not data extents.

--

With Best Regards,
Marat Khalili