if e2fs is saying that the first backup superblock is at 32768 why do you multiply it by 4 to get the 'real super block backup location? Why doesn't e2fs do the multiplication to give the 'real' location? Is that a bug? If so I think that can be easily fixed. Not by me ( don't have the know-how) but by some one who knows how to program.

On Mon, Feb 20, 2012 at 8:59 AM, Matt Graham <danceswithcrows@usa.net> wrote:
From: Michael Havens <bmike1@gmail.com>
> "sudo e2fsck -b block_number /dev/xxx"
> The first backup superblock was at 131072. Are other
> backup blocks located every 131072?

No.

 dumpe2fs  /dev/mapper/vg-usr32 | grep 'Backup super'
 Backup superblock at 32768
 Backup superblock at 98304
 Backup superblock at 163840
 Backup superblock at 229376
[snip]

Multiply those by 4, and you see the first backup is 131072, second is 393216,
third is 655360, fourth is 917504, and they're spread even farther apart as
they go up.  A 7.9G filesystem here has 8 backup superblocks, while a 50G
filesystem has 11.  I'm not sure how the copies are distributed, but there's
probably a fairly simple algorithm in the source for mke2fs that describes it.


--
Matt G / Dances With Crows
The Crow202 Blog:  http://crow202.org/wordpress/
There is no Darkness in Eternity/But only Light too dim for us to see

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