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ECC matters

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Re: ECC matters

#561

Post by sitkack »

tyoma wrote: post #338
nostrademons wrote: post #237

I still remember Craig Silverstein being asked what his biggest mistake at Google was and him answering "Not pushing for ECC memory." Google's initial strategy (c. 2000) around this was to save a few bucks on hardware, get non-ECC memory, and then compensate for it in software. It turns out this is a terrible idea, because if you can't count on memory being robust against cosmic rays, you also can't count on the soft…

Figure this is as good of a time as any to ask this: There are many various DRAMs in a server (say, for disk cache). Has Google or anyone who operates at a similar scale seen single bit errors in these components?

Yes.

Bit flips (for all reasons) occur in buses, registers, caches, etc. Anything that has state can have state changed incorrectly.

This is why filesystems like ZFS exist and storage formats have pervasive checksums.

Re: ECC matters

#562

Post by sitkack »

loeg wrote: post #440
cturner wrote: post #406

Earlier quoted context omitted.

The TDP on EPYC chips is a lot higher. I think of Threadripper as mid-tier, and EPYC as the high-end. Ryzen is remarkable because you can buy new equipment with ECC, at consumer prices. I am hazy, but don't think that has been possible since the 386 era ('parity ram').

> The TDP on EPYC chips is a lot higher. EPYC TDP ranges from "a lot lower" (35W embedded, 120W regular) up to "comparable with" (180-240W, a single 280W model) relative to Threadripper (180-250W last gen; current gen is all 280W). It's definitely not a lot higher on the Epyc side. > I think of Threadripper as mid-tier, and EPYC as the high-end. This oversimplifies to the point of not being a useful intuition (or is…

AMD is more accurate in their TDP specs than Intel is, they can't really be compared.

Re: ECC matters

#563

Post by smegger001 »

buran77 wrote: post #528
behringer wrote: post #526

Earlier quoted context omitted.

Users most definitely want it. They just aren't technically literate enough to know about it. Hello user, for an extra 10 dollars, would you like to guarantee that cosmic radiation never affects your computing experience, including having to reformat, reinstall, or otherwise reboot your phone/computer randomly when one day something just doesn't work anymore? Was it an update? Was it cosmic radiation? Was it a bad ca…

Indeed, users don't know enough to care but more than that, for most users this is simply not a problem because they haven't been practically affected. Most may never experience a bit flip, and most of the flips won't be obvious anyway (e.g. no visible effect). So your hypothetical dialogue will sound more like a scam to a regular user. You're charging money to tackle a problem they don't have or see, only addressing…

>So your hypothetical dialogue will sound more like a scam to a regular user. You're charging money to tackle a problem they don't have or see,

I don't know the same argument could be made and ecc be swapped with surge protectors and people still purchase those.

Re: ECC matters

#564

Post by loeg »

sitkack wrote: post #562
loeg wrote: post #440

Earlier quoted context omitted.

> The TDP on EPYC chips is a lot higher. EPYC TDP ranges from "a lot lower" (35W embedded, 120W regular) up to "comparable with" (180-240W, a single 280W model) relative to Threadripper (180-250W last gen; current gen is all 280W). It's definitely not a lot higher on the Epyc side. > I think of Threadripper as mid-tier, and EPYC as the high-end. This oversimplifies to the point of not being a useful intuition (or is…

AMD is more accurate in their TDP specs than Intel is, they can't really be compared.

This is not responsive to he comment you're replying to, which is comparing AMD to AMD.

Re: ECC matters

#565

Post by sitkack »

loeg wrote: post #564
sitkack wrote: post #562

Earlier quoted context omitted.

AMD is more accurate in their TDP specs than Intel is, they can't really be compared.

This is not responsive to he comment you're replying to, which is comparing AMD to AMD.

My comment was corrupted by rowhammer. Not only was it misdirected, the content is also probably wrong.

Re: ECC matters

#566

Post by alkonaut »

xxs wrote: post #559
alkonaut wrote: post #552

Earlier quoted context omitted.

That's more a hypothetical " if ECC was common enough that the products would exist" scenario. The current status is that it mostly doesn't exist outside OEM parts. Searching an online retailer for ECC brings me hundreds of results for "non-ECC" RAM. When they occasionally have 1-2 products with ECC, they aren't as aggressively binned as the non-ECC sticks. They'll have higher latencies and lower clock frequencies. B…

ECC could have been common, if there was a meaningful CPU support for. Intel basically did - "you need Xeon to do exactly what an i7 does + ECC, it just costs 5 times more... We just fused the ECC part of memory controller of i7, so buy Xeon." The entire discussion is about why ECC is not common and why ECC matters. There is no technical reason for ECC to be uncommon aside purposed market segmentation. Of course, the…

Completely agree. I'm not avoding it because I don't think it' s worth it in theory. It's because it'snot worth it in practice, right now. Because you basically either have to buy something slower, or can't buy it at all.

Re: ECC matters

#567

Post by usefulcat »

detaro wrote: post #135
usefulcat wrote: post #114

Earlier quoted context omitted.

It’s not. I have a low end Epyc machine with ECC. It has a TDP of something like 30 watts.

what kind of machine is that? Been vaguely looking for one a while back, and everything seemed difficult to get (since the main target is large-volume customers I guess)

Sorry, I didn't see this earlier. It's Supermicro board with an Epyc 3201 (8c/8t), base frequency is ~1.5 Ghz. There's no CPU fan, so it can get quite hot. It throttles at 94 degrees celcius, and it will hit that if more than around 4-6 cores are being fully used. However there are options in the bios to disable some of the cores. In my case I've disabled 4 of the cores and the temperature is much more reasonable now.
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