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Should I buy ECC memory? (2015)

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Re: Should I buy ECC memory? (2015)

#91

Post by user5994461 »

hashhar wrote: post #23
ddingus wrote: post #5

Yes. Bit errors are uncommon and range from benign to crash. Your storage has them, memory has them, network has them. Non error correcting memory very significantly increases risk. And this is the kind of risk you don't notice, until you do and when you do, it's often subtle, insidious, impossible to track down. Servers absolutely. It's debatable on desktop, but we have huge RAM now. Might as well error correct. The…

I won't bother on a desktop. I've been using 4 machines for the last 17 years with storage varying from 10GB to 2TB and RAM varying from 128MB to 16GB and haven't personally seen any kind of data corruption in motion (or at rest for that matter). Only had 2 mechanical drives fail (though predictably). ECC is costly. The memory modules itself and the board required to support it properly.

I have been seeing numerous memory corruption on many of my computers, including end of life memory sticks and motherboards that died before my eyes.

At work, including my sysadmin years, up to a very long time ago on stupid summer jobs fixing computers, I have spent countless man*months to debug issues that were ultimately caused by memory errors. All of that could have been avoided by using ECC.

Re: Should I buy ECC memory? (2015)

#92

Post by colanderman »

sytelus wrote: post #55
nostrademons wrote: post #7

While I was at Google, someone asked one of the very early Googlers (I think it was Craig Silverstein, but it may've been Jeff Dean) what was the biggest mistake in their Google career, and they said "Not using ECC memory on early servers." If you look through the source code & postmortems from that era of Google, there are all sorts of nasty hacks and system design constraints that arose from the fact that you could…

Google had done extensive studies[1]. There is roughly 3% chance of error in RAM per DIMM per year. That doesn't justify buying ECC if you have just one personal computer to worry about. However if you are in data center with 100K machines each with 8 DIMM, you are looking at about 6K machines experiencing RAM errors each day . Now if data is being replicated then these errors can propogate corrupted data in unpredic…

> There is roughly 3% chance of error in RAM per DIMM per year. […] with 100K machines each with 8 DIMM, you are looking at about 6K machines experiencing RAM errors each day.

Can you work out the math? I don't follow it. 3%×100K×8÷365=66 per day by my reasoning…

Re: Should I buy ECC memory? (2015)

#93

Post by binarycrusader »

snuxoll wrote: post #45
binarycrusader wrote: post #17

Earlier quoted context omitted.

Not true with Ryzen, as long as you find unregistered ECC acceptable. Somewhat not true with Intel, as some of the lower end Xeons now support it.

AFAIK all of the Xeon chips support ECC, every Xeon E3 chip (which uses the desktop socket) I've looked at includes it.

Sorry, I was a little obtuse. What I was inferring was that historically, only higher-priced server chips from Intel had ECC support. In 2013, Intel launched the v3 lower-end Xeon E3s server chips that were closer to the price of the consumer Intel chips and offer ECC with comparable clock speeds. Of course, all of those only have 4 cores instead of 8.

Yes, all of the E3s support ecc, but Xeon's didn't always support ECC until the launch of the Xeon E3 as far as I can tell.

Re: Should I buy ECC memory? (2015)

#94

Post by michaelmrose »

user5994461 wrote: post #86
loeg wrote: post #72

Earlier quoted context omitted.

> There is roughly 3% chance of error in RAM per DIMM per year. That doesn't justify buying ECC if you have just one personal computer to worry about. How do you make that leap?

It's an inappropriate leap. Consumers should have ECC memory too. However the consumer market has long decided to settle for ECC nowhere and cheap everywhere. ECC hardware comes at premium option that can easily be +100%. You need support in the memory, the motherboard and the CPU. Given the price difference, personal computers will have to live with the memory errors. People will not pay double for their computers.…

Amd has modestly priced hardware that supports ecc

Re: Should I buy ECC memory? (2015)

#95

Post by lomnakkus »

derefr wrote: post #78
lomnakkus wrote: post #38

Earlier quoted context omitted.

Indeed. It's true that the data may be corrupted before hitting any disk[1], but once it has hit the disks (>1), it's extremely unlikely that you'll ever hit a similar bit error where it'll mistakenly choose the wrong disk block to recover from. The main point of e.g. ZFS or Btrfs checksumming is that a) at least it isn't getting worse , and b) I can tell if it's getting worse. [1] ... but if the bits are not generat…

> The number of people who religiously check PGP signatures/SHA256sums or whatever is miniscule. • If you transfer things around using BitTorrent, it'll ensure you always end up with a file that hashes correctly to the sum it originally had when the .torrent file was constructed. • Many archive formats (zip, rar, and 7z, at least) contain checksums, and archival utilities validate those checksums during extraction, r…

True. Still mostly immaterial in the grand scheme of things, I think?

EDIT: Should say, as a point of interest: Even though .zip's were protected back in the Good Old Days, that didn't really matter because we all got corrupted (expanded from .zip) .mp3's because of those fucking RTL3xxsomething cards that would just transmit things perfectly and then corrupt the checksum (or whichever way 'round). Ugh. One of the few times I've actually hated engineers.

(Don't get me wrong. I really do want more of these checks to be pervasive. We start with our local file systems.)

Re: Should I buy ECC memory? (2015)

#97

Post by veidr »

Yes. Everybody reading this should use ECC RAM, and non-ECC RAM should be called "error-propagating RAM".

Random bit flips aren't cool, and they happen regularly. Most computers that have ECC RAM can report whether errors happen. I see them at least once a year or so. For instance, here are 2 ECC-correctable memory errors that occurred just last month.

Cosmic rays? Fukushima phantom? Who knows. You'll never know why they happen (unless it's like a bad RAM module and they happen a lot), but if you don't rock ECC you will never know they happened at all. You'll be left guessing when, years later, some encrypted file can no longer decrypt, and all the backups show the same corruption...

[1]: https://www.dropbox.com/s/zndvy3nkv1jipri/2017-03-20%20FUCK%...

[2]: https://www.dropbox.com/s/6yeoedc7ajzq4u9/2017-03-20%20FUCK%...

Re: Should I buy ECC memory? (2015)

#98

Post by esun »

spullara wrote: post #57

I reproduced this by bit-squatting cloudfront.net after reading about it. So many memory errors! http://dinaburg.org/bitsquatting.html Loved the variety as well. Sometimes though requests came to me the Host header was correct!

Fascinating article. Did you ever find a reason for the different ios results?

Re: Should I buy ECC memory? (2015)

#100

Post by lomnakkus »

derefr wrote: post #79
lomnakkus wrote: post #68

Earlier quoted context omitted.

zpool scrub (This may be a myth: It's not something you should actually do that often because actually reading the media may dregrade it.)

Either way, it'd be fine on SSDs, then?

Hm? As long as the error correction technology on your chosen SSD of choice stands up, I guess... yes? What, exactly, are you asking?
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