Messages in this thread | | | Subject | Re: [OT] Redundancy eliminating file systems, breaking MD5, donating money to OSDL | From | Valdis.Kletnieks@vt ... | Date | Fri, 16 Jan 2004 15:37:42 -0500 |
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On Fri, 16 Jan 2004 15:22:39 EST, Timothy Miller <miller@techsource.com> said:
> Think about it! If we had a filesystem that actually DID this, and it > was in the Linux kernel, it would spread far and wide. It's bound to > happen that someone will identify a collision. We then report that to > the committee offering the reward and then donate it to OSDL to help > Linux development.
Actually, it's *not* "bound to happen". Figure out the number of blocks you'd need to have even a 1% chance of a birthday collision in a 2**128 space.
And you'd need that many disk blocks on *a single system*.
Then figure out the chances of a collision on a small machine that only has 20 or 30 terabytes (yes, in this case terabytes is small).
The whole reason "use MD5 as a check for identical blocks" is useful is because the chances of *that* going wrong are vanishingly small compared to the chances that a memory stick will throw an undetected multiple-bit error, or that a RAID controller will write blocks to the wrong disks, or any number of other things that *do* happen in real life, but rarely enough that we don't bother writing code to defend against them.
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