Re: RAID10 total capacity incorrect

[Hugo Mills <hugo@carfax.org.uk>]

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On Sun, Jun 02, 2013 at 05:52:38PM +0100, Tim Eggleston wrote:
> Hi Hugo,
> 
> Thanks for your reply, good to know it's not an error as such (just
> me being an idiot!).
> 
> >Additional space will be allocated from the available unallocated
> >space as the FS needs it.
> 
> So I guess my question becomes, how much of that available
> unallocated space do I have? Instinctively the btrfs df output feels
> like it's missing an equivalent to the "size" column from vanilla
> df.

   Look at btrfs fi show -- you have "size" and "used" there, so the
difference there will give you the unallocated space.

> Is there a method of getting this in a RAID situation? I understand
> that btrfs RAID is more complicated than md RAID, so it's ok if the
> answer at this point is "no"...

   Not in any obvious (and non-surprising) way. Basically, any way you
could work it out is going to give someone a surprise because they
were thinking of it some other way around. The problem is that until
the space is allocated, the FS can't know how that space needs to be
allocated (to data/metadata, or with what replication type and hence
overheads), so we can't necessarily give a reliable estimate.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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         --- If you're not part of the solution, you're part ---         
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