F2FS Superblock Locations

F2FS Superblock Locations

[Zachary]

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Hello,

Recently I was checking the file format for F2FS and noticed that the
superblocks' location on the partition was both at the beginning.  This
means that if a large portion of the partition is corrupted, then it is
possible for both superblocks to be destroyed.  From my understanding of
other filesystems, they prevent that by spreading out the superbolock
backups across the partition so that it reduces the chances of all
superblocks being destroyed.  Has this been noticed before or am I mistaken
in some way?

Thank you,
Zachary Winnerman

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Re: F2FS Superblock Locations

[Jaegeuk Kim]

Hi,

2013-10-30 (수), 21:06 -0400, Zachary:
> Hello,
> 
> Recently I was checking the file format for F2FS and noticed that the
> superblocks' location on the partition was both at the beginning.
> This means that if a large portion of the partition is corrupted, then
> it is possible for both superblocks to be destroyed.  From my
> understanding of other filesystems, they prevent that by spreading out
> the superbolock backups across the partition so that it reduces the
> chances of all superblocks being destroyed.  Has this been noticed
> before or am I mistaken in some way?

IMHO, traditional rotational disks like HDDs need such the superblock
backups.

But for the solid-state disks like SSDs and eMMCs, I suspect that the
backups are needed in practical, since its firmware, FTL, spreads the
data across the whole NAND arrays to avoid cell errors (e.g., wear-out).
So I think the superblock is very much hard to be broken especially on
flash storages.

Thank you,


-- 
Jaegeuk Kim
Samsung



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Re: F2FS Superblock Locations

[Zachary]

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This was in reference to software mistakes that might wipe portions of the
disk rather than hardware failures, it came up after I almost had one
though it turns out its an unrelated problem.
On Oct 30, 2013 9:56 PM, "Jaegeuk Kim" <jaegeuk.kim@samsung.com> wrote:

> Hi,
>
> 2013-10-30 (수), 21:06 -0400, Zachary:
> > Hello,
> >
> > Recently I was checking the file format for F2FS and noticed that the
> > superblocks' location on the partition was both at the beginning.
> > This means that if a large portion of the partition is corrupted, then
> > it is possible for both superblocks to be destroyed.  From my
> > understanding of other filesystems, they prevent that by spreading out
> > the superbolock backups across the partition so that it reduces the
> > chances of all superblocks being destroyed.  Has this been noticed
> > before or am I mistaken in some way?
>
> IMHO, traditional rotational disks like HDDs need such the superblock
> backups.
>
> But for the solid-state disks like SSDs and eMMCs, I suspect that the
> backups are needed in practical, since its firmware, FTL, spreads the
> data across the whole NAND arrays to avoid cell errors (e.g., wear-out).
> So I think the superblock is very much hard to be broken especially on
> flash storages.
>
> Thank you,
>
>
> --
> Jaegeuk Kim
> Samsung
>
>

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------------------------------------------------------------------------------
Android is increasing in popularity, but the open development platform that
developers love is also attractive to malware creators. Download this white
paper to learn more about secure code signing practices that can help keep
Android apps secure.
http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk

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Re: F2FS Superblock Locations

[Jaegeuk Kim]

2013-10-30 (수), 23:33 -0400, Zachary:
> This was in reference to software mistakes that might wipe portions of
> the disk rather than hardware failures, it came up after I almost had
> one though it turns out its an unrelated problem.

If this is due to the SW mistakes, it would be better to rewrite the
superblock only by mkfs.f2fs, since the superblock contains just static
information of its partition.
I can simply add an option to do that in mkfs.f2fs.

But, if the checkpoint is corrupted, there is no way to recover.
Thanks,
> 
> On Oct 30, 2013 9:56 PM, "Jaegeuk Kim" <jaegeuk.kim@samsung.com>
> wrote:
>         Hi,
>         
>         2013-10-30 (수), 21:06 -0400, Zachary:
>         > Hello,
>         >
>         > Recently I was checking the file format for F2FS and noticed
>         that the
>         > superblocks' location on the partition was both at the
>         beginning.
>         > This means that if a large portion of the partition is
>         corrupted, then
>         > it is possible for both superblocks to be destroyed.  From
>         my
>         > understanding of other filesystems, they prevent that by
>         spreading out
>         > the superbolock backups across the partition so that it
>         reduces the
>         > chances of all superblocks being destroyed.  Has this been
>         noticed
>         > before or am I mistaken in some way?
>         
>         IMHO, traditional rotational disks like HDDs need such the
>         superblock
>         backups.
>         
>         But for the solid-state disks like SSDs and eMMCs, I suspect
>         that the
>         backups are needed in practical, since its firmware, FTL,
>         spreads the
>         data across the whole NAND arrays to avoid cell errors (e.g.,
>         wear-out).
>         So I think the superblock is very much hard to be broken
>         especially on
>         flash storages.
>         
>         Thank you,
>         
>         
>         --
>         Jaegeuk Kim
>         Samsung
>         

-- 
Jaegeuk Kim
Samsung



------------------------------------------------------------------------------
Android is increasing in popularity, but the open development platform that
developers love is also attractive to malware creators. Download this white
paper to learn more about secure code signing practices that can help keep
Android apps secure.
http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk
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