Re: Btrfs: wipe all the superblock [redhat bugzilla 889888]

[Goffredo Baroncelli <kreijack@tiscalinet.it>]

Hi hugo

On 01/07/2013 07:24 PM, Hugo Mills wrote:
[...]

>>     print "Superblock #%d - %20d - '%s'"%(i,pos,sign)
>>
>> $ python extract-sign.py
>> Superblock #0 -                65600 - '_BHRfS_M'
> 
> 64 KiB

OK, (above)
> 
>> Superblock #1 -             67108928 - '_BHRfS_M'
> 
> 256 MiB

.... above is 64M, below is 256M !
> 
>> Superblock #2 -         274877907008 - '_BHRfS_M'
> 
> 1 TiB
> 
>> Superblock #3 -     1125899906842688 - ''
> 
> 4 PiB
> 
>> Superblock #4 -  4611686018427387968 - ''
> 
> 16 EiB

Not reachable in linux. There is a VFS limits to 8EB.
> 
> 
>> To me it seems that in a 7TB filesystem there is only 3 superblocks.
> 
>    That would be as expected. How many on a 5 PiB filesystem, though?
> Or a 20 EiB one?

I wrote 7TB, but I meant 8EB. I first tried a test with 7TB and I wrote
the email, but then I retested with 8EB and I corrected the email,
forgetting some 7t instead of 8e...

Anyway, if BTRFS would allow more than three super-block,  in the 7TB
case, the super-block at 1TB would appeared
> 
>    Hugo.
> 


-- 
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