On Mon, Sep 7, 2015 at 11:58 AM, Chris Murphy <li...@colorremedies.com> wrote:
> On Sat, Sep 5, 2015 at 4:42 AM, Hugo Mills <h...@carfax.org.uk> wrote:
>> On Sat, Sep 05, 2015 at 12:13:30PM +0200, Ivan Petrovic wrote:
>
>>> So you're saying that I can't make first and third partition to work
>>> with it's data? Maybe I'll try with btrfs-restore, do you think it can
>>> rescue this 2 drives?
>>
>>    Unlikely. Like I said, if the FS was using single storage for
>> everything, a random 33% of the filesystem has gone away. There's
>> probably not enough of it left to make anything coherent.
>
> With single profile for everything, is metadata and data guaranteed to
> be co-located on the same device? If not, then there's no way for this
> to be recovered. If they are, then I think recovery would depend on
> the system chunk always being device-n mirrored, which we don't have.

Sorry. In single device failure, raid1 system chunk is possible and
might help. But to be able to recover data from any surviving drive
(n-1 failures) would mean each device has a copy of the system chunk,
in addition to guaranteed co-location of data and metadata chunks.


-- 
Chris Murphy
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