Re: BTRFS Raid 5 Space missing - ideas ?

Andrei Borzenkov
2019-04-21T04:40:06Z

20.04.2019 23:19, Adam Borowski пишет:
> On Sat, Apr 20, 2019 at 12:46:16PM +0200, Juergen Sauer wrote:
>> I wish a happy Easer Days before :)
>
> Same to you!
>
>> During my tests with BTRFS as Raid5 setup, I found a courious little
>> "problem".
>
>> Total devices 3 FS bytes used 9.98TiB
>> devid 1 size 9.09TiB used 4.99TiB path /dev/sdb1
>> devid 2 size 5.46TiB used 4.99TiB path /dev/sdc1
>> devid 3 size 5.46TiB used 4.99TiB path /dev/sde1
>
>> All patitioins sdb1 sdc1 sde1 are the same size: 9.0 TiB. But BTRFS ist
>> not using the bigger space on sdc1, sde1, there is only 5.46 TiB used,
>> even there are 9.0 Tib Avaible, so 4.0 TiB are unused.
>
> It's working as expected: while btrfs does RAID per block group rather than
> per whole block device, there's no way to place a raid5 block group in a way
> that doesn't require at least 3 devices. This means with a 3-disk setup the
> space utilized will be only as big as the smallest one.
>

But as reported, all drives were replaced by larger ones but only one
drive shows increased size: "All patitioins sdb1 sdc1 sde1 are the same
size".