Re: btrfs raid1 on 16TB goes read-only after "btrfs: block rsv returned -28"

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On Wed, Jun 05, 2013 at 04:59:57PM +0100, Martin wrote:
> On 05/06/13 16:43, Hugo Mills wrote:
> > On Wed, Jun 05, 2013 at 04:28:33PM +0100, Martin wrote:
> >> btrfs fi df:
> >> 
> >> Data, RAID1: total=2.85TB, used=2.84TB Data: total=8.00MB,
> >> used=0.00 System, RAID1: total=8.00MB, used=412.00KB System:
> >> total=4.00MB, used=0.00 Metadata, RAID1: total=27.00GB,
> >> used=25.82GB Metadata: total=8.00MB, used=0.00
> >> 
> >> 
> >> btrfs fi show:
> >> 
> >> Label: 'bu-16TB_0'  uuid: 8fd9a0a8-9109-46db-8da0-396d9c6bc8e9 
> >> Total devices 4 FS bytes used 2.87TB devid    4 size 3.64TB used
> >> 1.44TB path /dev/sdf devid    3 size 3.64TB used 1.44TB path
> >> /dev/sde devid    1 size 3.64TB used 1.44TB path /dev/sdc devid
> >> 2 size 3.64TB used 1.44TB path /dev/sdd
> > 
> 
> Thanks for that. I can give kernel 3.9.4 a try. For a giggle, I'll try
> first with "nice 19" and syncs in a loop...
> 
> 
> One confusing bit is why the "Data, RAID1: total=2.85TB" from "btrfs
> fi df"?

   Because you've got enough raw space allocated for 2.85 TiB of data;
that's 5.7 TiB of actual bytes, because you're using RAID-1 for it.
That should add up to somewhere near the total of the "used" values in
btrfs fi show. The difference will be accounted for in metadata,
system, and the inevitable rounding errors. All the values are shown
in powers-of-two -- i.e. IEEE units, not SI units despite the use of
SI prefixes.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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