Tracking Down a Single-Bit RAM Error

Hanji writes "We have discussed here before the potential effects of and protections against cosmic ray radiation, but for the average computer user, it's an obscure threat that doesn't affect them in any real way. Well, here's a blog post that describes a strange segfault and, after extensive debugging, traces it down to a single bit flip, probably caused by a stray cosmic ray. Lots of helpful descriptions of Linux debugging techniques in this one, and a pretty clear demonstration that this can be a real problem. I know I'm never buying a desktop without ECC RAM ever again!" The author acknowledges that it might not have been a cosmic ray-based error, but the troubleshooting steps are interesting no matter what the cause.

Comments

Re:RAM error?

[History's Coming To]

Aha, my plan worked perfectly *rubs hands in delight*. I hack the entire internet at once by flipping single bits on a large number of machines. The maths is kind of chaotic. It's fun to track viruses as ant-algorithm analogies too.

Cosmic Ray Protection...

[r00tyroot]

I'm putting tinfoil hats on all of my servers, right away!

Re:erm....

[sakdoctor]

My RAM is shielded against cosmic rays by my mothers basement.

Re:RAM error?

[Anonymous Coward]

Just goes to show you, computers are a bit pedantic.

Re:RAM error?

[Rinikusu]

/*After years of successful operation a Perl script quite working*/

And a bit flipped to an e?

Re:All data channels are noisy

[Anonymous Coward]

you pay boku bucks for it

Is "boku" some sort of retarded mangling of beaucoup?

Re:erm....

[Thing 1]

My girlfriend at the time even made me a tinfoil hat, that I'd sometimes wear around the house as I babbled nonsense about impending alien invasions. :)

I am both shocked and amazed that you eventually broke up.

Re:Also

[Scaba]

Then there's the fact that bits aren't even stored as bits really. All current drives use (E)PRML which is (Enhanced) Partial Response Maximum Likelihood. What this means is bits aren't encoded as a high-low state or FM wave or any of that. They are written using flux reversals, but the level is not carefully controlled, it can't be. So when you read the data the drive actually looks at an analogue wave. It encodes the partial response it gets, and then finds the maximumly likely pattern that matches.

I doubt this is true. The disk would have to be spinning at 88 mph in order to activate the flux capacitor, and the power brick would need to supply 1.21 gigawatts to the drive, which exceeds the capacity of even the most tricked-out gaming PC. I think you'd better check your science, my friend.

Re:All data channels are noisy

[StikyPad]

Walla!

Re:All data channels are noisy

[Chris Burke]

Uh, no, not at all... *shifty eyes*

Re:Cosmic rays, my ass. Occam's Razor time.

[bitflip]

It was me.

Sorry 'bout that.

Re:erm....

[fishexe]

You live below your mother's basement???

Sure. In his mother's sub-basement.

+1 Informative

[fishexe]

I shouldn't have spent all my mod points yesterday. I guess my hardware knowledge is obsolete; I had no idea modern HDDs don't store individual bits anymore.

windows crashes

[prkamath]

And we used to blame Microsoft engineering team for all the crashes we experienced !!

Re:RAM error?

[petsounds]

And 10,000 years from now, your Perl script has become the complete works of Shakespeare...

Re:Takes me back

[Jurily]

larger programs to fail too frequently

We showed him right, huh?

My userid, FTW!

[RandomBitFlipper]

Woohoo!