Re: [RFC] TileFS - a proposal for scalable integrity checking

["Jörn Engel" <joern@lazybastard.org>]

On Sat, 28 April 2007 17:05:22 -0500, Matt Mackall wrote:
> 
> Some things we need to check during fsck:
> 
>  all directories point to in-use inodes
>  all in-use inodes are referred to by directories
>  all inodes in use are marked in use
>  all free inodes are marked free
>  all inodes point to in-use blocks
>  all inode refcounts are correct
>  all inode block counts are correct
>  free inode count is correct
> 
>  no blocks are used twice
>  all used blocks are marked as used
>  all free blocks are marked as free
>  optional: all block contents are correct

   statfs information matches filesystem content

This one may still require a full fsck in your current approach.  One if
the good aspects of ChunkFS (assuming my understanding matches reality)
is to have per-chunk counters for free blocks, free inodes, etc.  For a
fast fsck you would need to have these counters per-unit as well.  It
doesn't matter whether your unit is a tile, chunk, blockgroup or
karboozel.

Having some tree structure for these counters would also help.  Statfs
requires to add all counters for all units.  Smaller units speed up fsck
but slow down statfs.  With a tree statfs can be O(log(n)).

Jörn

-- 
"Translations are and will always be problematic. They inflict violence
upon two languages." (translation from German)
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