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

[Andi Kleen <andi@firstfloor.org>]

Matt Mackall <mpm@selenic.com> writes:

> This is a relatively simple scheme for making a filesystem with
> incremental online consistency checks of both data and metadata.
> Overhead can be well under 1% disk space and CPU overhead may also be
> very small, while greatly improving filesystem integrity.

Problem I see is that your scheme doesn't support metadata checksums only.
IMHO those are the most interesting because they have the potential
to be basically zero cost, unlike full data checksumming.
And doing metadata checksums is enough to handle the fsck
problem.

I'm sure there are many cases where full checksumming makes sense too,
but those shouldn't be forced on everybody because it will slow down
some important workloads (like O_DIRECT)

Metadata checksums would be best just put into the file systems
data structures. Essentially every object (inode, extent, directory entry,
super block) should have a checksum that can be incrementially updated.

-Andi