3 ms·

What do people think ECC is going to do for them, and what do they think will happen when an ECC event is triggered?

AshamedCaptain 3y ago
I suppose they'll claim that it's what doesn't trap which is important, e.g. what can be (silently) corrected by ECC would normally result in silent corruption without ECC.
CTDOCodebases 3y ago
What I think it will do for me? Correct single bit errors and alert me to them.
- gambiting 3y ago
  Like, in what way - you get a windows popup saying "hey, just detected a bit error, but it was corrected, all good"? Because if yes, you'd get such a popup daily, and I'm not sure what the actual value of it is. And I'm not being funny, I literally don't see the value of it(of the notification, not the correcting).
  - dale_glass 3y ago
    You don't get a popup. In Linux, it's logged in dmesg. In Windows I imagine it goes in the system log. The system keeps on running. The value of the notification is that if most days you get nothing and suddenly 5000 corrected errors pop up, you know something is not quite right as of late. Maybe you're overdoing the overclocking. Maybe the module isn't sitting quite well in the slot. Maybe a solder joint is failing. If you have a 2 bit memory error, the typical result is a BSOD/kernel oops. Which is a good thing actually. It means you know for sure your RAM is bad, and it prevents any faulty data from being written anywhere. So rather than possibly propagating the error is just stopped. I believe there have been systems that try to handle it more elegantly. Kill the process the memory belongs to if it's a non-essential one then permanently blacklist that block to ensure it's not used again.
    - deleted 3y ago
      [deleted]
  - CTDOCodebases 3y ago
    > Like, in what way - you get a windows popup saying "hey, just detected a bit error, but it was corrected, all good"? No I've set it up so I get an email. > Because if yes, you'd get such a popup daily I doubt that. There was a study done at Google that reported 8% of DIMMs encountered at least one memory error per year[0]. > I'm not sure what the actual value of it is. I like my PC to be as deterministic as possible[1] so if my programs crash I don't want to have to turn it off and test the memory which takes hours[2]. [0] - https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf [1] - https://blog.cskr.dev/posts/corrupt-backup/ https://blog.cskr.dev/posts/corrupt-backup/ [2] - https://www.youtube.com/watch?v=0itrM7t4l34 https://www.youtube.com/watch?v=0itrM7t4l34
adrian_b 3y ago
On a computer configured correctly, the errors are logged and the user or administrator may be notified when they happen. In my experience the most valuable benefit of ECC is the detection of aged memory modules. All modern DRAM has a limited lifetime. Hopefully that lifetime is more than 5 years, but there are always some modules that may reach end-of-life much faster, especially on computers that are always on. While on a new memory module it would be abnormal for memory errors to happen more frequently than a few times per year, on an aged module errors may happen many times per day, or even many times per hour. I have encountered a few such cases that happened after several years of continuous using. Due to ECC I was notified about the errors and I could replace the offending modules before them becoming so bad as to guarantee data corruption. Another reason is that even if ECC cannot prevent a RowHammer attack, it makes pretty certain that a RowHammer attack will be detected immediately (because the attacker cannot control the location of the flipped bits, and even if there are many errors, so they will be miscorrected, in most cases they will still be detected and logged and the administrator should always be instantly notified when there are two or more errors per day, as this will never happen normally).
- musicale 3y ago
  My thought also when I first heard about RowHammer - how do you avoid triggering an ECC error? It seemed like you'd need multiple bit flips, possibly of specific bits.
RecycledEle 3y ago
I had a stick of RAM go bad in an old Socket 775 motherboard, but since it was one of 6 sticks of RAM, it only affected the PC on rare occasions. That PC was flaky for years before I pulled out some RAM to upgrade and found the problem had been fixed. When a similar problem occurred on a PC with ECC RAM, I got a warning message saying memory errors had been detected that repeated a few times, then I got a message saying one stick of RAM had been deactivated and that I could keep running. The Dell T3500 dropped from 24 GB to 20 GB and did not even need to be rebooted. That is why I love ECC RAM and Xeon processors. I know if there is a problem and can wait to fix it. I can buy used RAM and processors with confidence that the BIOS self rests will tell me what is good and what is bad.

I suppose they'll claim that it's what doesn't trap which is important, e.g. what can be (silently) corrected by ECC would normally result in silent corruption without ECC.

CTDOCodebases 3y ago

What I think it will do for me? Correct single bit errors and alert me to them.

gambiting 3y ago
Like, in what way - you get a windows popup saying "hey, just detected a bit error, but it was corrected, all good"? Because if yes, you'd get such a popup daily, and I'm not sure what the actual value of it is. And I'm not being funny, I literally don't see the value of it(of the notification, not the correcting).
- dale_glass 3y ago
  You don't get a popup. In Linux, it's logged in dmesg. In Windows I imagine it goes in the system log. The system keeps on running. The value of the notification is that if most days you get nothing and suddenly 5000 corrected errors pop up, you know something is not quite right as of late. Maybe you're overdoing the overclocking. Maybe the module isn't sitting quite well in the slot. Maybe a solder joint is failing. If you have a 2 bit memory error, the typical result is a BSOD/kernel oops. Which is a good thing actually. It means you know for sure your RAM is bad, and it prevents any faulty data from being written anywhere. So rather than possibly propagating the error is just stopped. I believe there have been systems that try to handle it more elegantly. Kill the process the memory belongs to if it's a non-essential one then permanently blacklist that block to ensure it's not used again.
  - deleted 3y ago
    [deleted]
- CTDOCodebases 3y ago
  > Like, in what way - you get a windows popup saying "hey, just detected a bit error, but it was corrected, all good"? No I've set it up so I get an email. > Because if yes, you'd get such a popup daily I doubt that. There was a study done at Google that reported 8% of DIMMs encountered at least one memory error per year[0]. > I'm not sure what the actual value of it is. I like my PC to be as deterministic as possible[1] so if my programs crash I don't want to have to turn it off and test the memory which takes hours[2]. [0] - https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf [1] - https://blog.cskr.dev/posts/corrupt-backup/ https://blog.cskr.dev/posts/corrupt-backup/ [2] - https://www.youtube.com/watch?v=0itrM7t4l34 https://www.youtube.com/watch?v=0itrM7t4l34

adrian_b 3y ago

On a computer configured correctly, the errors are logged and the user or administrator may be notified when they happen. In my experience the most valuable benefit of ECC is the detection of aged memory modules. All modern DRAM has a limited lifetime. Hopefully that lifetime is more than 5 years, but there are always some modules that may reach end-of-life much faster, especially on computers that are always on. While on a new memory module it would be abnormal for memory errors to happen more frequently than a few times per year, on an aged module errors may happen many times per day, or even many times per hour. I have encountered a few such cases that happened after several years of continuous using. Due to ECC I was notified about the errors and I could replace the offending modules before them becoming so bad as to guarantee data corruption. Another reason is that even if ECC cannot prevent a RowHammer attack, it makes pretty certain that a RowHammer attack will be detected immediately (because the attacker cannot control the location of the flipped bits, and even if there are many errors, so they will be miscorrected, in most cases they will still be detected and logged and the administrator should always be instantly notified when there are two or more errors per day, as this will never happen normally).

musicale 3y ago
My thought also when I first heard about RowHammer - how do you avoid triggering an ECC error? It seemed like you'd need multiple bit flips, possibly of specific bits.

RecycledEle 3y ago

I had a stick of RAM go bad in an old Socket 775 motherboard, but since it was one of 6 sticks of RAM, it only affected the PC on rare occasions. That PC was flaky for years before I pulled out some RAM to upgrade and found the problem had been fixed. When a similar problem occurred on a PC with ECC RAM, I got a warning message saying memory errors had been detected that repeated a few times, then I got a message saying one stick of RAM had been deactivated and that I could keep running. The Dell T3500 dropped from 24 GB to 20 GB and did not even need to be rebooted. That is why I love ECC RAM and Xeon processors. I know if there is a problem and can wait to fix it. I can buy used RAM and processors with confidence that the BIOS self rests will tell me what is good and what is bad.