Re: size 2.73TiB used 240.97GiB after balance

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-07-08 15:06, Donald Pearson wrote:
> I wouldn't use dd.
>
> I would use recover to get the data if at all possible, then you can
> experiment with try to fix the degraded condition live.  If you have
> any chance of getting data from the pool, you reduce that chance every
> time you make a change.
>
> If btrfs did the balance like you said, it wouldn't be raid5.  What
> you just described is raid4 where only one drive holds parity data.  I
> can't say that I actually know for a fact that btrfs doesn't do this,
> but I'd be shocked and some dev would need to eat their underware if
> the balance job didn't distribute the parity also.
>
That is correct, it does distribute the parity among all the member 
drives.  That said, it would still have to modify the existing drives 
even if it did put the parity on just the new drive, because raid{4,5,6} 
are defined as _striped_ data with parity, not mirrored (ie, if you just 
removed the parity, you'd have a raid0, not a raid1).



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